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Cell Structure and Function in the Bacteria and Archaea

Cell Structure and Function in the Bacteria and Archaea

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4.1 DiversityNOT Among FOR the SALE and OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 1. The Bacteria are classified into several Structure major phyla. 2. The Archaea are currently classified into two major phyla. © Jones4.2 Cell & Shapes Bartlett and Learning,Arrangements LLC and© Jones & FunctionBartlett Learning, LLC NOT FOR3. ManySALE bacterial OR cells DISTRIBUTION have a rod, spherical, or NOT FOR SALE OR DISTRIBUTION spiral shape and are organized into a specific cellular arrangement. 4.3 An Overview to Bacterial and Archaeal in the Bacteria Cell Structure 4. Bacterial and archaeal cells© Jonesare organized & Bartlettat Learning, LLC © Jones & Bartlett Learning, LLC the cellular and molecularNOT levels. FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4.4 External Cell Structures and Archaea 5. Pili allow cells to attach to surfaces or other cells. 6. Flagella provide . 7. A protects against , Our planet has always been in the “Age of Bacteria,” ever since attaches© Jones cells to surfaces, & Bartlett and helps Learning, LLCthe first —bacteria© of Jones course—were & Bartlett entombed Learning, in rocks LLCmore pathogensNOT evade FOR the SALE .OR DISTRIBUTIONthan 3 billion years ago. NOTOn any FOR possible, SALE reasonable OR DISTRIBUTION criterion, 4.5 The Cell Envelope bacteria are—and always have been—the dominant forms of 8. Bacterial cell walls help maintain cell shape and protect the from rupture. on . 9. Archaeal cell walls have crystalline layers. —Paleontologist Stephen J. Gould (1941–2002) © Jones10. & Molecules Bartlett and Learning, cross the cell LLC membrane © Jones & Bartlett Learning, LLC by facilitated or . “Double, double toil and trouble; Fire burn, and cauldron bubble” is NOT FOR11. ArchaealSALE membranes OR DISTRIBUTION are structurally unique. NOT FOR SALE OR DISTRIBUTION 4.6 The Cell and Internal the refrain repeated several by the chanting witches in Shakespeare’s Structures Macbeth (Act IV, Scene 1). This image of a hot, boiling cauldron actually 12. The contains the cell’s essential describes the environment in which many bacterial, and especially genetic information. archaeal, happily grow! For example, some species can be 13. contain nonessential© Jones genetic & Bartlettisolated Learning, from LLChot springs or the hot, acidic© mudJones pits & of Bartlett volcanic ventsLearning, LLC information. NOT FOR SALE ORFIGURE DISTRIBUTION 4.1 NOT FOR SALE OR DISTRIBUTION 14. , microcompartments, and ( ). inclusions carry out specific intracellular When the eminent evolutionary and geologist Stephen functions. J. Gould wrote the opening quote of this chapter, he as as most 15. Cytoskeletal regulate had no idea that embedded in these “bacteria” was and help determine cell shape. another whole of . Thanks to the pioneering studies MICRO©I NQUIRYJones 4: The& BartlettProkaryote/ Learning, LLC © Jones & Bartlett Learning, LLC ModeNOTl FOR SALE OR DISTRIBUTIONof and his colleagues,NOT FOR it SALE now is OR quite DISTRIBUTION evident there are two distinctly different groups of “”—the Bacteria and the Archaea (see Chapter 3). Many of the organisms Woese and others studied are organisms that would live a happy life in a witch’s cauldron

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(A) (B) FIGURE 4.1 Life at the Edge. Bacterial and archaeal have been isolated from the edges of natural cauldrons, including (A) the Grand © JonesPrismatic & Bartlett Spring inLearning, Yellowstone National LLC Park, Wyoming, where the ©water Jones of the hot& springBartlett is over Learning, 70ºC, or (B) the LLC mud pools surrounding sulfurous NOT FORsteam SALE vents ofOR the SolfataraDISTRIBUTION Crater in Pozzuoli, Italy, where the mudNOT has a veryFOR low SALEpH and a ORtemperature DISTRIBUTION above 90ºC. »» How do extremophiles survive under these extreme conditions?

because they can grow© atJones high temperatures,& Bartlett Learning, as different LLC from each other as they are© Jonesfrom the & Bartlett Learning, LLC produce gas,NOT or survive FOR inSALE extremely OR DISTRIBUTIONEukarya. NOT FOR SALE OR DISTRIBUTION acidic and hot environments—a real cauldron! Termed extremophiles, these members of the As more microbes have had their complete domains Bacteria and Archaea have a unique sequenced, it now is clear that there are genetic makeup and have adapted to extreme envi- unique as well as shared characteristics between © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC ronmental conditions. species in the domains Bacteria and Archaea. InNOT fact, Gould’s FOR SALE “first fossils” OR DISTRIBUTION may have been In this chapter,NOT we examine FOR SALE briefly OR some DISTRIBUTION archaeal species. Many microbiologists believe of the organisms in these two domains. However, the of today’s archaeal species might because so many of humans are in represent a type of that first inhabited the domain Bacteria, we emphasize structure © Jonesplanet & Bartlett Earth whenLearning, it was LLCa young, hot place. within© Jonesthis domain. & Bartlett As we Learning,see in this chapter, LLC NOT FORThese SALE unique OR characteristics DISTRIBUTION led Woese to propose a studyNOT of FOR the structural SALE OR features DISTRIBUTION of bacterial these organisms be lumped together and called the cells provides a window to their activities and Archaebacteria (archae = “ancient”). illustrates how the Bacteria relate to other living Since then, the domain name has been organisms. changed to Archaea because (1) not all members As we examine bacterial (and archaeal) cell are extremophiles or ©related Jones to these& Bartlett possible Learning, structure, LLC we can assess the dogmatic© statement Jones & Bartlett Learning, LLC ancient ancestors and (2)NOT they FOR are not SALE Bacteria— OR DISTRIBUTIONthat these cells are characterized byNOT a lack FOR of a SALE OR DISTRIBUTION they are Archaea. Some might also debate using and internal membrane-bound - the term prokaryotes when referring to both elles. Before you finish this chapter, you will be domains, as organisms in the two domains are equipped to revise this view. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4.1 Diversity Among the Bacteria and Archaea In this section, we discuss bacterial and archaeal bacterial and archaeal species and a suspected diversity using the current classification scheme, 10 million species. In this section, we will high- © Joneswhich & Bartlett is based Learning, in large LLCpart on light© a Jonesfew phyla & andBartlett groups Learning, using the phyloge- LLC NOT FORsequence SALE data.OR DISTRIBUTION There are some 7,000 known neticNOT tree inFOR FIGURE SALE 4.2 . OR DISTRIBUTION

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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ARCHAEA BACTERIA (2 major phyla) (>25 major phyla) © Jones & Bartlett Learning, LLC © Jones & BartlettExtreme Learning, LLC Gram-positive NOT FORbacteria SALE OR DISTRIBUTIONChlamydia MethanogensNOT FOR SALE OR DISTRIBUTION

Proteobacteria

Spirochaetes © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning,Eukarya LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Hyperthermophiles

LAST UNIVERSAL © Jones & Bartlett Learning, LLC © Jones & BartlettCOMMON ANCESTORLearning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION FIGURE 4.2 The of Bacteria and Archaea. The tree shows several of the bacterial and archaeal lineages discussed in this chapter. »» What is common to the branch base of both the Bacteria and Archaea?

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC The NOTDomain FOR Bacteria SALE ORContains DISTRIBUTION Some They can be isolatedNOT from FOR Arctic SALE ice, thermal OR DISTRIBUTIONhot of the Most Studied Microbial springs, the fringes of , and the tissues of ani- Organisms mals. Bacterial species, along with their archaeal KEY CONCEPT relatives, have so completely colonized every part 1. The Bacteria are classified into several major phyla. of the Earth that their mass is estimated to out- © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC weigh the mass of all and combined. NOT FORThere SALE are OR about DISTRIBUTION 25 assigned phyla of Bacteria Let’sNOT look FOR briefly SALE at some OR of theDISTRIBUTION major phyla and that have been identified from culturing or other groups. Chapter 10 will focus more deeply nucleotide . It should come as no on Bacteria and Archea diversity. to you by now to read that the vast major- . The Proteobacteria (proteo © Jones & Bartlett Learning,ity of these LLC phyla play a positive role© in Jones & =Bartlett “first”) contains Learning, the largest LLC and most diverse group NOT FOR SALE OR DISTRIBUTION(MICROFOCUS 4.1). Although not uniqueNOT to FOR just SALEof species OR and DISTRIBUTION includes many familiar gram-negative the , they digest into sim- genera, such as ( FIGURE 4.3A ). The ple chemicals; they extract from the air also contains some of the most recog- and make it available to plants for pro- nized human pathogens, including species of duction; they break down the remains of all that , , (responsible for die and© Jonesrecycle the& Bartlett and Learning, other elements; LLC ), © (responsible Jones & forBartlett ), Learning, and LLC and theyNOT produce FOR SALEoxygen ORgas thatDISTRIBUTION we and other (responsibleNOT for ). FOR SALE It is likely OR thatDISTRIBUTION animals breathe. the mitochondria of the Eukarya were derived Of course, we know from Chapter 1 and per- through endosymbiosis from an of the sonal experience that some bacterial organisms are Proteobacteria (see MicroInquiry 3). harmful—many human pathogens are members The group also includes the rickettsiae : © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC An organism onNOT or in FORof SALE the domain OR DISTRIBUTION Bacteria. Certain species multiply (sing.,NOT ), FOR SALE which OR cannot DISTRIBUTION reproduce with- which a infects. within the , where they disrupt tissues out infecting a host cell. These tiny bacterial cells or produce that result in . are transmitted among humans primarily by : The Bacteria have adapted to the diverse envi- , and are cultivated only in living tissues An having jointed ronments on Earth, inhabiting the air, , and such as chick embryos. Different species cause a © Jonesappend ages& Bartlett and seg- Learning, LLC © Jones & Bartlett Learning, LLC mented body (e.g., , water, and they exist in enormous numbers on number of important , including Rocky NOTlice, FOR , SALE mosquitoes). OR DISTRIBUTIONthe surfaces of virtually all plants andNOT animals. FOR SALEMountain OR spotted DISTRIBUTION and fever.

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Mélanie Hamon, an assistante de recherché at the Institut Pasteur in Paris, says that when she intro- duces herself as a , she often is asked, “Just what does that mean?” To help explain her discipline, she gives us,© inJones eight letters, & Bartlett what she Learning, calls “some demystifyingLLC facts about bacteria.”© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION asic principles: Their average size is 1/25,000th of an inch. In other words, hundreds of thou- Bsands of bacteria fit into the period at the end of this sentence. In comparison, human cells are 10 to 100 times larger with a more complex inner structure. While human cells have copious amounts of membrane-contained subcompartments, bacteria more closely resemble pocketless sacs. Despite their© simplicity, Jones they& Bartlett are self-contained Learning, living LLC beings, unlike , which ©depend Jones on a &host Bartlett cell to Learning, LLC carryNOT out their FOR life SALEcycle. OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION stonishing: Bacteria are the of the evolutionary , the source of all living organisms. AQuite successful evolutionarily speaking, they are ubiquitously distributed in soil, water, and extreme environments such as ice, acidic hot springs or . In the human body, bacteria account for 10% of dry weight, populating mucosal surfaces of the oral cavity, , © Jones &urogenital Bartlett tract Learning, and surface LLC of the . In fact, bacteria are© Jonesso numerous & Bartlett on earth that Learning, scientists LLC NOT FOR estimateSALE ORtheir DISTRIBUTIONbiomass to far surpass that of the rest of allNOT life combined. FOR SALE OR DISTRIBUTION rucial: It is a little known fact that most bacteria in our bodies are harmless and even essential Cfor our survival. Inoffensive skin settlers form a protective barrier against any troublesome invader while approximately 1,000 species of gut colonizers work for our benefit, synthesizing , breaking down complex© nutrientsJones &and Bartlett contributing Learning, to gut immunity. LLC Unfortunately for babies© Jones & Bartlett Learning, LLC (and parents!), we are born with a sterile gut and “colic” our way through bacterial colonization. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ools: Besides the profitable relationship they maintain with us, bacteria have many other practical Tand exploitable properties, most notably, perhaps, in the production of , and . Less widely known are their industrial applications as factories, , sewage processors, degraders, and so forth. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC vil: Unfortunately, not all bacteria are “good,” and those that cause disease give them all an often EundeservedNOT FOR and SALE unpleasant OR reputation. DISTRIBUTION If we consider the multitude of mechanismsNOT FOR these SALE “bad” OR DISTRIBUTION bacteria—pathogens—use to assail their host, it is no wonder that they get a lot of bad press. Indeed, millions of years of coevolution have shaped bacteria into organisms that “know” and “predict” their hosts’ responses. Therefore, not only do bacterial toxins know their target, which is never missed, but bacteria can predict their host’s and often avoid it. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEesistant: OR Even DISTRIBUTION more worrisome than their effectivenessNOT at targeting FOR SALEtheir host OR is their DISTRIBUTION faculty to Rwithstand antibiotic therapy. For close to 50 years, have revolutionized in their ability to treat bacterial . Unfortunately, overuse and misuse of antibiotics have led to the alarming fact of resistance, which promises to be disastrous for the treatment of such diseases. ngenious: The appearance of antibiotic-resistant bacteria is a reflection of how adaptable they are. IThanks to their large© populations Jones & they Bartlett are able Learning, to mutate their LLC genetic makeup, or even exchange© Jones it, & Bartlett Learning, LLC to find the appropriateNOT combination FOR SALEthat will ORprovide DISTRIBUTION them with resistance. Additionally, bacteriaNOT FOR SALE OR DISTRIBUTION are able to form “,” which are cellular aggregates covered in slime that allow them to tolerate applications that normally eradicate free-floating individual cells. long tradition: Although “little ” were first observed in the , it was not A©until Jones the 1850s & Bartlettthat Louis PasteurLearning, fathered LLC modern . From this© Jonespoint forward, & Bartlett research Learning, LLC on bacteria has developed into the flourishing it is today. For many years to come, researchers will NOTcontinue FOR to delve SALE into ORthis intricateDISTRIBUTION world, trying to understand how theNOT good FORones can SALE help and OR DISTRIBUTION how to protect ourselves from the bad ones. It is a great honor to be part of this tradition, working in the very place where it was born.

1Republished with permission of the author, the Institut Pasteur, and the Pasteur Foundation. The original article © Jones &appeared Bartlett in Pasteur Learning, Perspectives LLC Issue 20 (Spring 2007), the newsletter© Jones of the & Pasteur Bartlett Foundation, Learning, which may LLC be NOT FOR SALEfound at www.pasteurfoundation.orgOR DISTRIBUTION © Pasteur Foundation. NOT FOR SALE OR DISTRIBUTION

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(C) (D)

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(E)(F) FIGURE© 4.3 Jones Members & Bartlett of the Domain Learning, Bacteria. ( ALLC) (Bar = 10 µm.),© ( BJones) & Bartlett aureus Learning, LLC (Bar =NOT 10 µm.), FOR (C) SALE OR (Bar = 2 µm.), (D) species (Bar NOT= 20 µm.), FOR (E) SALEAnabaena ORspecies DISTRIBUTION (Bar = 100 µm.), and (F) pallidum (Bar = 10 µm.). All images are light micrographs except (C), a false-color scanning micrograph. »» What is the Gram result for E. coli and S. aureus?

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEFirmicutes. OR DISTRIBUTION The (firm = “strong”; eraNOT Staphylococcus FOR SALE and OR DISTRIBUTION are responsible cuti = “skin”) consists of many species that are gram- for several mild to life-threatening human illnesses positive. As we will see in this chapter, they share a ( FIGURE 4.3B ). similar thick “skin,” which refers to their Also within the Firmicutes is the structure. Genera include and , Myco plasma, which lacks a cell wall but is other- © Jones & Bartlett Learning,specific species LLC of which are responsible© for Jones & wiseBartlett phylogenetically Learning, related LLC to the gram-positive NOT FOR SALE OR DISTRIBUTIONand botulism, respectively. Species withinNOT the FORgen- SALEbacterial OR species DISTRIBUTION ( FIGURE 4.3C ). Among the small-

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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORest SALEfree-living OR bacterial DISTRIBUTION organisms, one species in fact,NOT some FOR of SALEthe first OR animalcules DISTRIBUTION seen by causes a form of (Chapter 20) while were probably spirochetes from another mycoplasmal illness represents a sexually- his teeth scrapings (see Chapter 1). Among transmitted disease (Chapter 24). the human pathogens are , . Another phylum of gram- the causative agent of and one of the positive species is the© Actinobacteria Jones & Bartlett. Often Learning, most common LLC sexually transmitted© Jonesdiseases & Bartlett Learning, LLC called the “actinomycetes,”NOT these FOR soil SALE organisms OR DISTRIBUTION( FIGURE 4.3F ; Chapter 24) and specificNOT species FOR SALE OR DISTRIBUTION form a system of branched filaments that some- of , which are transmitted by ticks or lice what resemble the growth form of fungi. The genus and are responsible for Lyme disease and relaps- Streptomyces is the source for important antibiotics ing fever (Chapter 23). ( FIGURE© 4.3D Jones). Another & Bartlett medically Learning, important genus LLC Other Phyla. There© Jones are many & Bartlett other phyla Learning, LLC is ,NOT FOR one SALE species OR of whichDISTRIBUTION is respon- within the domain NOTBacteria. FOR Several SALE lineages OR DISTRIBUTION sible for . branch off near the root of the domain. The com- Cyanobacteria. In Chapter 3 we discussed mon link between these organisms is that they are the cyanobacteria. They are phylogenetically hyperthermophiles; they grow at high tempera- related to the gram-positive species and can exist tures (70°C–85°C). Examples include and © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC as unicellular, filamentous, or colonial forms , which typically are found in earthly NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ( FIGURE 4.3E ). Once known as blue-green algae cauldrons such as hot springs and other hydro- because of their pigmentation, pigments also may thermal sites. be black, yellow, green, or red. The periodic red- ness of the Red , for example, is due to blooms CONCEPT AND REASONING CHECKS Bloom: of those cyanobacterial© species Jones that & contain Bartlett large Learning, 4.1 What LLC three unique events occurred© within Jones the & BartlettA sudden increase Learning, in LLC Proteobacteria and Cyanobacteria that contributed the number of cells amounts of red pigment.NOT FOR SALE OR DISTRIBUTIONto the of the Eukarya and theNOT -rich FOR SALEof an organism OR DISTRIBUTION in The phylum Cyanobacteria is unique among on Earth? an environment. bacterial groups because its members carry out similar to unicellular algae (Chapter 6) using the light-trapping pigment chlo- rophyll.© TheirJones evolution & Bartlett on Earth Learning, was responsible LLC The Domain Archaea© Jones Contains & Bartlett Learning, LLC for theNOT “oxygen FOR revolution” SALE OR that DISTRIBUTIONtransformed life Many ExtremophilesNOT FOR SALE OR DISTRIBUTION on the young planet some 2 billion years ago. In KEY CONCEPT 2. The Archaea are currently classified into two addition, probably are derived from major phyla. the endosymbiotic union with a cyanobacterial © Jonesancestor & Bartlett (see MicroInquiry Learning, 3).LLC © Jones & Bartlett Learning, LLC Classification within the domain Archaea has NOT FOR SALEChlamydiae. OR DISTRIBUTION Roughly half the size of the NOT FOR SALE OR DISTRIBUTION rickettsiae, members of the phylum been more difficult than within the domain are so small that they cannot be seen with the light Bacteria, in large part because they have not been and are cultivated only within living studied as long as their bacterial counterparts. cells. Most species in the phylum are pathogens Archaeal organisms are found throughout and one species causes© the Jones gonorrhea-like & Bartlett dis- Learning,the . LLC Many genera are extremophiles,© Jones & Bartlett Learning, LLC ease known as chla mydia.NOT Chlamydial FOR SALE diseases OR DISTRIBUTIONgrowing best at environmental extremes,NOT FORsuch SALE OR DISTRIBUTION are described in Chapter 24. as very high temperatures, high concentra- . The phylum Spirochaetes tions, or extremes of pH. However, most species contains more than 340 gram-negative species exist in very cold environments although there that possess© Jones a unique & Bartlett cell body Learning, that coils into LLC a are archaeal genera that© Jones thrive under & Bartlett more mod- Learning, LLC long helixNOT and FOR moves SALE in a corkscrew OR DISTRIBUTION pattern. The est conditions as well.NOT The archaealFOR SALE genera OR can DISTRIBUTIONbe ecological niches for the spirochetes is diverse: placed into one of two major phyla. from free-living species found in mud and sedi- Euryarchaeota. The Euryarchaeota contain ments, to symbiotic species present in the diges- organisms with varying , many being tive tracts of insects, to the pathogens found in extremophiles. Some groups, such as the metha- © Jonesthe & Bartletturogenital Learning, tracts of vertebrates. LLC Many spi- nogens© Jones (methano & =Bartlett “methane”; Learning, gen = “produce”) LLC NOT FORrochetes SALE are OR found DISTRIBUTION in the human oral cavity; are killedNOT by FOR oxygen SALE gas and OR therefore DISTRIBUTION are found in

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FIGURE 4.4 Members of the Domain Archaea. (A) A false-color electron micrograph of the hungatei. (Bar = 0.5 µm.) (B) An aerial view above Redwood City, California, of the salt ponds whose color is due to high concentrations of extreme halophiles. (C) A false-color scanning electron © Jones & Bartlett Learning, LLCmicrograph of , a © Jones & thatBartlett grows in Learning, waters as hot as LLC 90ºC. (Bar = 0.5 µm.) »» What advantage is afforded these species that grow in such (C) NOT FOR SALE OR DISTRIBUTIONextreme environments? NOT FOR SALE OR DISTRIBUTION

environments devoid of oxygen gas. The produc- The fourth group are the . © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC tion of methane (natural) gas is important in their Not only do they grow at high temperatures like NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION ( FIGURE 4.4A ). In fact, these the hyperthermophiles, they also grow at very archaeal species release more than 2 billion tons low pHs. of methane gas into the atmosphere every year. Crenarchaeota. The second phylum, the About a third comes from the archaeal species Crenarchaeota, are mostly hyperthermophiles, living© in Jones the & Bartlett () Learning, of cows. LLC typically growing in ©hot Jones springs and& Bartlett marine hydro- Learning, LLC AnotherNOT FOR group SALE is the OR extreme DISTRIBUTION halophiles thermal vents ( FIGURENOT 4.4C FOR). Other SALE species OR are dis-DISTRIBUTION (halo = “salt”; phil = “loving”). They are distinct persed in open , often inhabiting the cold from the in that they require oxy- waters (–3°C) of the deep sea environments gen gas for energy metabolism and need high and polar . © Jones &concentrations Bartlett Learning, of salt (up LLCto 30% NaCl) to grow © TABLEJones 4.1 & summarizes Bartlett Learning, some of the LLC charac- NOT FORand SALE reproduce. OR DISTRIBUTION The fact that they often contain teristicsNOT thatFOR are SALE shared ORor are DISTRIBUTION unique among the pink pigments makes their identification easy three domains. ( FIGURE 4.4B ). In addition, some extreme halo-

philes have been found in lakes where the pH is CONCEPT AND REASONING CHECKS greater than 11. 4.2 Compared to the more moderate environments in © Jones & Bartlett Learning,A third LLC group is the hyperthermophiles© Jones & Bartlettwhich Learning,some archaeal species LLC grow, why have others NOT FOR SALE OR DISTRIBUTIONthat grow optimally at temperatures aboveNOT 80°C. FOR SALEadapted OR DISTRIBUTIONto such extreme environments?

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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR TABLESALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4.1 Some Major Differences Between Bacteria, Archaea, and Eukarya Characteristic Bacteria Archaea Eukarya Cell nucleus No No Yes © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC form Single, circular Single, circular Multiple, linear proteins presentNOT FOR SALE ORNo DISTRIBUTIONYes Yes NOT FOR SALE OR DISTRIBUTION cell wall Yes No No Membrane -linked -linked Ester-linked sedimentation value 70S 70S 80S Ribosome© Jones sensitivity & Bartlett to Learning, NoLLC Yes © Jones Yes& Bartlett Learning, LLC FirstNOT amino FOR in SALE a protein OR DISTRIBUTIONFormylmethionine MethionineNOT FOR SALE OR DISTRIBUTION Chlorophyll-based photosynthesis Yes (cyanobacteria) No Yes (algae) Growth above 80°C Yes Yes No Growth above 100°C No Yes No Pathogens Yes No Yes © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

4.2 Cell Shapes and Arrangements Bacterial and archaeal cells© Jones come in & a Bartlettbewildering Learning, denote a LLCrod-shaped bacterial cell, and© as Jones a genus & Bartlett Learning, LLC assortment of sizes, shapes,NOT FORand arrangements, SALE OR DISTRIBUTIONname (Bacillus). NOT FOR SALE OR DISTRIBUTION reflecting the diverse environments in which they A spherically shaped bacterial cell is known grow. As described in Chapter 3, these three char- as a (pl., cocci; kokkos = “berry”) and tends acteristics can be studied by viewing stained cells to be quite small, being only 0.5 µm to 1.0 µm in with the light microscope. Such studies show that diameter. Although they are usually round, they also © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC most, including the clinically significant ones, may be oval, elongated, or indented on one side. appearNOT in one FOR of three SALE different OR DISTRIBUTIONshapes: the rod, Many bacterial NOTspecies FOR that SALEare cocci OR stay DISTRIBUTION the sphere, or the spiral. together after division and take on cellular arrange- ments characteristic of the species ( FIGURE 4.5B ). Variations in Cell Shape and Cocci remaining in a pair after reproducing rep- © JonesCell & Bartlett Arrangement Learning, Exist LLC resent© aJones & Bartlett. The organism Learning, that LLCcauses NOT FORKEY SALE CONC EPTOR DISTRIBUTION gonorrhea,NOT FOR Neisseria SALE gonorrhoeae, OR DISTRIBUTION and one type of 3. Many bacterial cells have a rod, spherical, or spi- bacterial (N. meningitidis) are diplococci. ral shape and are organized into a specific cellular Cocci that remain in a chain are called strepto- arrangement. coccus. Certain species of streptococci are involved in strep throat () and tooth A bacterial cell with a rod© Jonesshape is &called Bartlett a bacil- Learning,decay (S. mutans),LLC while other species are© Jonesharmless & Bartlett Learning, LLC lus (pl., ). In variousNOT species FOR of SALE rod-shaped OR DISTRIBUTIONenough to be used for producing dairyNOT products FOR SALE OR DISTRIBUTION bacteria, the cylindrical cell may be as long as such as yogurt (S. lactis). Another arrangement of 20 µm or as short as 0.5 µm. Certain bacilli are cocci is the tetrad, consisting of four cocci forming slender, such as those of Salmonella typhi that cause a square. A cube-like packet of eight cocci is called typhoid© fever;Jones others, & Bartlett such as the Learning, agent of anthrax LLC a (sarcina = “bundle”).© Jones & Bartlett luteus, Learning, a LLC (BacillusNOT anthracis), FOR SALEare rectangular OR DISTRIBUTION with squared common inhabitant NOTof the FORskin, isSALE one example. OR DISTRIBUTION ends; still others, such as the diphtheria bacilli Other cocci may divide randomly and form an ( diphtheriae), are club shaped. irregular grape-like cluster of cells called a staphylo- Most rods occur singly, in pairs called diplobacil- coccus (staphylo = “cluster”). A well-known exam- lus, or arranged into a long chain called strepto- ple, , is often a cause of © Jonesbacillus & Bartlett (strepto Learning, = “chains”) (LLCFIGURE 4.5A ). Realize poisoning,© Jones toxic & shock Bartlett syndrome, Learning, and several LLC skin NOT FORthere SALE are two OR ways DISTRIBUTION to use the word “bacillus”: to infections.NOT FOR The latter SALE are ORknown DISTRIBUTION in the modern

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 104 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION (A) Bacillus (rod) NOT FOR SALE OR DISTRIBUTION

© Jones & BartlettSingle Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Diplobacillus (pair)

© Jones & Bartlett Learning, LLC (chain) © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

(B) Coccus (sphere)

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Diplococcus (pair) NOT FOR SALE OR DISTRIBUTION Single NOT FOR SALE OR DISTRIBUTION

Tetrad © Jones &(group Bartlett of 4) Learning, LLC © Jones & Bartlett Learning, LLC Staphylococcus NOT FOR SALE OR DISTRIBUTION(cluster) NOT FOR SALE OR DISTRIBUTION

Streptococcus (chain) © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION(C) Spiral NOT FOR SALE OR DISTRIBUTION

Vibrio (comma-shaped) © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones & BartlettSpirochete Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

FIGURE 4.5 Variation in Shape and Cell Arrangements. Many bacterial and archaeal cells have a bacillus (A) or coccus (B) shape. Most spiral shaped-cells (C) are not organized into a specific arrangement (all bars = 10 μm.). »» In Panel C, identify the vibrio and the spirillum forms in the photograph. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION vernacular as “staph” infections. Notice again that ( FIGURE 4.5C ). The vibrio is a curved rod that the words “streptococcus” and “staphylococcus” can resembles a comma. The cholera-causing organ- be used to describe cell shape and arrangement, or ism is typical. Another spiral form a bacterial genus (Streptococcus and Staphylococcus). called spirillum (pl., spirilla) has a helical shape © Jones & Bartlett Learning,The third LLC common shape of bacterial© Jones cells & withBartlett a thick, Learning, rigid cell wall LLC and flagella that assist NOT FOR SALE OR DISTRIBUTIONis the spiral, which can take one of threeNOT forms FOR SALEmovement. OR DISTRIBUTIONThe spiral-shaped form known as

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.3 An Overview to Bacterial and Archaeal Cell Structure 105

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORspirochete SALE ORhas aDISTRIBUTION thin, flexible cell wall but no fla- NOTIn addition FOR to SALE the bacillus, OR DISTRIBUTION coccus, and spiral gella in the traditional sense. Movement in these shapes, other variations exist. Some bacterial spe- organisms occurs by contractions of endoflagella cies have appendaged bacterial cells while others that run the length of the cell (described later consist of branching filaments; and some archaeal in this chapter). The organism causing syphilis, species have square and star shapes. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Treponema pallidum, typifies a spirochete. Spiral- CONCEPT AND REASONING CHECKS shaped bacterial cells canNOT be from FOR 1 µm SALE to 100 OR µm DISTRIBUTION 4.3 Propose a reason why bacilli do not formNOT tetrads FOR or SALE OR DISTRIBUTION in length. clusters.

4.3© JonesAn Overview & Bartlett to BacterialLearning, andLLC Archaeal Cell Structure© Jones & Bartlett Learning, LLC In the lastNOT chapter FOR we SALE discovered OR thatDISTRIBUTION bacterial and Recent advances in understandingNOT FOR SALE bacterial OR and DISTRIBUTION archaeal cells appear to have little visible struc- archaeal indicate these organisms ture when observed with a light microscope. This, exhibit a highly ordered intracellular organiza- along with their small size, gave the impression tion. This organization is centered on three specific © Jonesthey & Bartlett are homogeneous, Learning, static LLC structures with an processes© Jones that need & Bartlett to be carried Learning, out ( FIGURE LLC 4.6 ). NOT FORorganization SALE OR very DISTRIBUTION different from eukaryotic cells. TheseNOT are: FOR SALE OR DISTRIBUTION However, the point was made that bacterial and archaeal species still have all the complex • Sensing and responding to the surround- processes typical of eukaryotic cells. It is simply a ing environment. Because most bacterial that, in most cases, the structure and some- and archaeal cells are surrounded by a cell times pattern to accomplish© Jones these processes & Bartlett is dif- Learning,wall, LLC some pattern of “external© structures” Jones & Bartlett Learning, LLC ferent from the membranousNOT organellesFOR SALE typical OR of DISTRIBUTIONis necessary to sense their environmentNOT FOR SALE OR DISTRIBUTION eukaryotic species. and respond to it or other cells such as for and motility. Cell Structure Organizes Cell Function • Compartmentation of metabolism. As KEY C©ON JonesCEPT & Bartlett Learning, LLC described in Chapter© Jones 3, &cell Bartlett metabolism Learning, LLC 4. BacterialNOT FORand archaeal SALE cells OR are DISTRIBUTION organized at the must be segregatedNOT FOR from SALE the exterior OR DISTRIBUTION cellular and molecular levels. environment and yet be able to transport

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Bacterial/archaeal cell is composed of External structures Cell envelope include© Jones & Bartlett Learning, LLC © Jonesincludes & Bartlett Learning, LLC Cytoplasm Cell wall Cell membrane Flagella NOT FORGlycocalyx SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION includes Pili Internal structures consists of Nucleoid include Capsule © Jones & Bartlett Learning, LLC Ribosomes© JonesInclusions & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Plasmids

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC FIGURE 4.6 A Concept Map for Studying Bacterial and Archaeal Cell Structure. Not all cells have all the structures shown here. »» Why can’t we NOT FORsee SALEin the TEM OR image DISTRIBUTION of a bacterial cell all the structures outlined inNOT the concept FOR map? SALE OR DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 106 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONmaterials to and from that environment.NOT FOR SALEing diseases OR DISTRIBUTIONlike strep throat are secreted from a In addition, protection from osmotic specific area of the surface. , which due to water movement into is the agent responsible for plague, contains a spe- cells must be in place. The “cell envelope” cialized apparatus through which toxic fulfills those roles. proteins are released. This apparatus only exists •© Growth Jones and& Bartlett . Learning, Cell survival LLC on the bacterial surface© Jones that is in& contactBartlett with Learning, the LLC NOTdemands FOR a complexSALE ORmetabolism DISTRIBUTION that occurs target host cells. NOT FOR SALE OR DISTRIBUTION within the aqueous “cytoplasm.” These pro- So, the cell biology studies are not only cesses and reproduction exist as internal important in their own right in understanding cell structures or subcompartments localized to structure, these studies also may have important © Jones & Bartlettspecific Learning, areas within LLCthe cytoplasm. significance© Jones to & clinical Bartlett microbiology Learning, and theLLC fight NOT FOR SALEOur understanding OR DISTRIBUTION of bacterial and archaeal againstNOT infectious FOR SALE disease. OR As DISTRIBUTION more is discovered cell biology is still an emerging field of study. about these cells and how they truly differ from However, there is more to cell structure than pre- eukaryotic cells, the better equipped we will be to viously thought—smallness does not equate with develop new antimicrobial agents that will target simplicity. the subcellular organization of pathogens. In an © Jones & Bartlett Learning,Although LLC this chapter is primarily© looking Jones at & eraBartlett when weLearning, have fewer LLC effective antibiotics to NOT FOR SALE OR DISTRIBUTIONbacterial cells at the cellular level, it alsoNOT is impor- FOR SALEfight infections, OR DISTRIBUTION understanding of cell structure tant to realize that bacterial and archaeal cells, like and function may be very important. their eukaryotic counterparts, are organized on On the following pages, we examine some of the molecular level as well. Specific cellular pro- the common structures found in an idealized bac- teins ©can Jones be localized & Bartlett to specific Learning, regions of the LLC cell. terial cell, as no single© Jonesspecies always& Bartlett contains Learning, all LLC For example,NOT FOR as the SALE name ORsuggests, DISTRIBUTION Streptococcus the structures ( FIGURENOT 4.7 ).FOR Our journeySALE ORstarts DISTRIBUTION by pyogenes has spherical cells. Yet many of the pro- examining the structures on or protruding from teins that confer its pathogenic nature in caus- the surface of the cell. Then, we examine the cell

© Jones & Bartlett Learning, LLC © JonesPili & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Cytoplasm Ribosome

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Flagella

© Jones & Bartlett Learning, LLC © Jones & BartlettGlycocalyx Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT CellFOR wall SALE OR DISTRIBUTION

Cell membrane

Nucleoid (with DNA) © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC FIGURE 4.7 . The structural features of a composite, “idealized” bacterial cell. Structures highlighted in blue are found in NOTall bacterialFOR SALEand archaeal OR species. DISTRIBUTION »» Which structures represent (a) externalNOT structures, FOR (b) SALEthe cell envelope, OR DISTRIBUTION and (c) cytoplasmic structures?

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.4 External Cell Structures 107

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORenvelope SALE before OR DISTRIBUTIONplunging into the cell cytoplasm. CONNOTCEPT FORAND REASONING SALE OR C HEDISTRIBUTIONCKS Note: images of cells give the impression of a static, 4.4 What is gained by bacterial and archaeal cells being motionless structure. Realize such images are but organized into three general sets of structures— external, envelope, and cytoplasmic? a “snapshot” of a highly active living cell. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4.4 External Cell Structures Bacterial and archaeal cells need to respond to and cells to the mucosal surface of the urogenital tract Mucosal: monitor their external environment. This is made whereas the adhesins on pertussis (caus- Referring to the mucous membranes lining many difficult© by Jones having & a cellBartlett wall that Learning, “blindfolds” LLC the ative agent of whooping© Jones ) adhere& Bartlett to cells Learning, of body cavities LLC exposed to cell. ManyNOT cells FOR have SALE solved ORthis sensingDISTRIBUTION problem the mucosal surface ofNOT the upper FOR respiratory SALE OR tract. DISTRIBUTION the environment. by possessing structures that extend from the cell In this way, the pili act as a factor by : surface into the environment. enhancing attachment to host cells, facilitating A pathogen-produced colonization, and possibly leading to dis- molecule or structure Pili Are Protein Fibers Extending ease development. Without the chemical moor- that allows the cell to © Jonesfr &om Bartlett the Cell Learning, Surface LLC © Jones & Bartlett Learning, LLC invade or evade the ing line lashing the bacterial cells to host cells, immune system and NOT FORKEY SALE CONC EPTOR DISTRIBUTION it is NOTless likely FOR the SALE cells couldOR DISTRIBUTION infect host tissue possibly cause disease. 5. Pili allow cells to attach to surfaces or other cells. (MICROFOCUS 4.2). Besides these attachment pili, some bacte- Numerous short, thin fibers, called pili (sing., rial species produce flexible conjugation pili ; pilus = “hair”), protrude from the surface © Jones & Bartlett Learning,that establish LLC contact between appropriate© Jones cells, & Bartlett Learning, LLC of most gram-negative bacteria ( FIGURE 4.8 ). The NOT FOR SALE OR DISTRIBUTIONfacilitating the transfer of genetic materialNOT FORfrom SALE OR DISTRIBUTION rigid fibers, composed of protein, act as a scaf- donor to recipient through a process called “con- folding onto which specific adhesive molecules, jugation” (Chapter 9). Conjugation pili are longer called adhesins, are attached at the tip. Therefore, than attachment pili and only one or a few are the function of pili is to attach cells to environ- produced on a cell. mental© surfaces Jones forming & Bartlett biofilms Learning, or, in the LLCcase Until recently, attachment© Jones pili& Bartlettwere thought Learning, LLC of humanNOT pathogens, FOR SALE to cell OR and DISTRIBUTION tissue surfaces. to be specific to onlyNOT certain FOR species SALE of OR gram- DISTRIBUTION This requires that the pili on different bacterial negative bacteria. However, extremely thin pili species have specialized adhesins to recognize the are present on at least some gram-positive bac- appropriate cell. For example, the pili adhesins on teria, including the pathogen Corynebacterium cells specifically anchor the diphtheriae and several Streptococcus species. © Jones & Bartlett Learning, LLC These© piliJones play &a veryBartlett similar Learning, role to the LLCpili on NOT FOR SALE OR DISTRIBUTION gram-negativeNOT FOR cells. SALE OR DISTRIBUTION It should be noted that microbiologists often use the term “pili” interchangeably with “fimbriae” (sing., ; fimbria = “fiber”). © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC CONCEPT AND REASONING CHECKS NOT FOR SALE OR DISTRIBUTION4.5 What would happen if pili lacked adhesins?NOT FOR SALE OR DISTRIBUTION

Flagella Are Long Appendages Extending from the Cell Surface © PiliJones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC KEY CONCEPT NOT FOR SALE OR DISTRIBUTION 6. Flagella provide motility.NOT FOR SALE OR DISTRIBUTION

Numerous species in the domains Bacteria and FIGURE 4.8 Bacterial Pili. False-color transmission Archaea are capable of some type of locomotion © Joneselectron & Bartlett micrograph Learning, of an Escherichia LLC coli cell (blue) with © Jones & Bartlett Learning, LLC many pili (green). (Bar = 0.5 µm.) »» What function do through liquids or over moist surfaces. This can be NOT FORpili SALEplay? OR DISTRIBUTION in theNOT form FOR of flagellar SALE motility OR DISTRIBUTIONor gliding motility.

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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION 4.2: PublicNOT Health FOR SALE OR DISTRIBUTION Doozies

They gathered at the clinical research center at Stanford University to do their part for the advancement of science (and earn a few dollars as well). They were the “sensational sixty”—sixty young men and women© Jones who would & Bartlett spend three Learning, days and nights LLC and earn $300 to help determine© Jones whether & Bartletthair-like Learning, LLC structurNOTes FOR called SALEpili have ORa significant DISTRIBUTION place in disease. NOT FOR SALE OR DISTRIBUTION A number of nurses and doctors were on hand to help them through their ordeal. The students would drink a fruit-flavored cocktail containing a special diarrhea-causing of Escherichia coli. Thirty students received cocktails that had E. coli with normal pili, while the other thirty had E. coli with pili mutated beyond repair. The hypothesis was that the bacterial cells with normal pili would latch onto © Jones & intestinalBartlett tissue Learning, and cause LLC diarrhea, while those with mutated© Jones pili would & Bartlettbe unable to Learning, attach and would LLC NOT FOR SALEbe swept OR away DISTRIBUTION by the rush of intestinal movements and notNOT cause FOR intestinal SALE distress. OR At DISTRIBUTION least that’s what the sensational sixty would either verify or prove false. On that fateful day in 1997, the experiment began. Neither the students nor the health professionals knew who was drinking the diarrhea cocktail and who was getting the “free pass”; it was a so-called double-blind experiment. Then came the waiting. Some experienced no symptoms, but others felt the © Jones & Bartlett Learning,bacterial LLC onslaught and clutched at their© lastJones remaining & Bartlett vestiges ofLearning, dignity. For some,LLC it was three days NOT FOR SALE OR DISTRIBUTIONof hell, with , abdominal cramps,NOT and numerous FOR SALE bathroom OR trips; DISTRIBUTION for others, luck was on their side, and investing in a lottery ticket seemed like a good idea. When it was all over, the numbers appeared to bear out the hypothesis: The great majority of volunteers who drank the mutated bacterial cells experienced no diarrhea, while the majority of those who drank the normal bacterial cells had attacks of diarrhea, in some cases real doozies. ©All Jonesappeared & to Bartlettprofit from Learning,the experience: LLC The scientists had some real-life© Jonesevidence that& Bartlett pili con- Learning, LLC tributeNOT to FORinfection; SALE the students OR DISTRIBUTION made their sacrifice to science and pocketedNOT $300 FOR each; andSALE the localOR DISTRIBUTION supermarket had a surge of profits from unexpected sales of toilet paper, Pepto-Bismol, and Imodium.

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Flagellar Motility. Many bacterial and ring in the cell wall, while gram-negative cells NOT FORar SALEchaeal ORcells DISTRIBUTIONare motile by using remarkable haveNOT a pair FOR of rings SALE embedded OR DISTRIBUTIONin the cell membrane “nanomachines” called flagella (sing., ). and another pair in the cell wall. Depending on the species, one or more flagella In the domain Archaea, flagellar protein com- may be attached to one or both ends of the cell, position and structure differs from that of the © Jones & Bartlett Learning,or at positions LLC distributed over the cell© Jones surface & Bacteria;Bartlett motility Learning, appears LLC similar though. NOT FOR SALE OR DISTRIBUTION( FIGURE 4.9A ). NOT FOR SALEThe OR basal DISTRIBUTION body represents a powerful biological Flagella range in length from 10 µm to motor or rotary engine that generates a propeller- 20 µm and are many times longer than the diam- type rotation of the rigid filament. The energy for eter of the cell. Because they are only about 20 nm rotation comes from the diffusion of protons (hydro- thick, they cannot be seen with the light micro- gen ions; H+) into the cell through proteins associ- scope© unless Jones stained. & Bartlett However, Learning, their existence LLC ated with the basal body.© Jones This energy & Bartlett is sufficient Learning, to LLC can beNOT inferred FOR by SALEusing dark-field OR DISTRIBUTION to produce up to 1,500NOT rpm byFOR the SALEfilament, OR driving DISTRIBUTION watch the live cells dart about. the cell forward. In the domain Bacteria, each flagellum is What advantage is gained by cells having fla- composed of a helical filament, hook, and basal gella? In nature, there are many chemical nutrients in © Jones &body Bartlett ( FIGURE Learning, 4.9B ). The hollow LLC filament is com- the© environment Jones & thatBartlett cells need Learning, to survive. CellsLLC will NOT FORposed SALE of ORlong, DISTRIBUTION rigid strands of protein while the searchNOT out FOR such attractantsSALE OR by DISTRIBUTION using their flagella to hook attaches the filament to a basal body (motor) move up the concentration gradient; that is, toward anchored in the cell envelope. the attractant. The process is called . Temporal sensing: The basal body is an assembly of more than 20 Being so small, the cells sense their chemical One that compares the different proteins that form a central rod and set surroundings using a temporal sensing system. © Joneschemical & environment Bartlett Learning, LLC © Jones & Bartlett Learning, LLC and concentration from of enclosing rings. Gram-positive cells have a pair In the absence of a gradient the cells undergo NOTone FOR moment SALE to the ORnext. DISTRIBUTIONof rings embedded in the cell membraneNOT and FOR one SALEa “random OR walking”DISTRIBUTION behavior. The flagella all

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.4 External Cell Structures 109

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Filament + H Hook

Outer membrane © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Cell wall Rotating Peptidoglycan layer NOT FOR SALE OR DISTRIBUTION basal NOT FOR SALE OR DISTRIBUTION body Cell membrane

+ H Cytoplasm

(A) (B) © JonesFIGURE & Bartlett 4.9 Bacterial Learning, Flagella. LLC(A) A light micrograph of stained © Jones vulgaris & s howingBartlett numerous Learning, flagella extending LLC from the cell surface. (Bar = NOT FOR10 µm.)SALE Note ORthat theDISTRIBUTION length of a flagellum is many times the widthNOT of the FORcell. (B )SALE The flagellum OR onDISTRIBUTION a gram-negative bacterial cell is attached to the cell wall and membrane by two pairs of protein rings in the basal body. »» Why is the flagellum referred to as a “nanomachine“?

rotate as a bundle counterclockwise and the cell called the “” (see below). Motility results Website Animation: moves straight ahead in© short Jones bursts & called Bartlett “runs” Learning, from the LLCtorsion generated on the cell© by Jones the nor- & BartlettBacterial Learning,Cell Motility LLC and Chemotaxis ( FIGURE 4.10A ). These runsNOT can FOR last aSALE few seconds OR DISTRIBUTIONmal rotation of the flagella. The resultingNOT motility FOR SALE OR DISTRIBUTION and the cells can move up to 10 body lengths is less regular and more jerky than with flagellar per second (the fastest human can run about 5–6 motility. body lengths per second). A reversal of flagellar Gliding Motility. Some bacterial cells can rotation (clockwise rotation) causes the cell to move about without flagella by gliding across a © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC “tumble” randomly for a second as the flagella solid surface. The motility occurs along the long becomeNOT unbundled FOR SALE and uncoordinated. OR DISTRIBUTION Then, axis of bacillus- or filamentous-shapedNOT FOR SALE cells OR and DISTRIBUTION the motor again reverses direction and another usually is slower than flagellar motility. The cya- run occurs in a new direction. nobacteria and (see Chapter 3) are If an attractant gradient is present, cell behav- two examples of organisms with gliding motility. © Jonesior & changesBartlett and Learning, the cells exhibit LLC “biased random ©How Jones the cells & actuallyBartlett move Learning, is not completely LLC NOT FORwalking.” SALE ORCells DISTRIBUTION moving up the gradient now understood.NOT FOR In some SALE cases, OR bacterial DISTRIBUTION cells rapidly experience longer periods when the motor turns extrude specialized pili at the front end (pole) of counterclockwise (lengthened runs) and shorter the cells. These pili attach to a surface and then periods when it turns clockwise (shortened tum- rapidly retract, which pulls the cell forward in a bles) ( FIGURE 4.10B ). The combined result is a net smooth or jerky motion. movement toward the ©attractant; Jones that& Bartlett is, up the Learning, CONCEPT LLC AND REASONING CHECKS © Jones & Bartlett Learning, LLC concentration gradient.NOT FOR SALE OR DISTRIBUTION4.6 Explain how flagella move cells during NOTa “run.” FOR SALE OR DISTRIBUTION Similar types of motile behavior are seen in photosynthetic organisms moving toward light () or other cells moving toward oxygen The Glycocalyx Is an Outer Layer gas (aerotaxis).© Jones M &ICRO BartlettFOCUS 4.3 Learning, investigates LLC how External to the Cell© Jones Wall & Bartlett Learning, LLC flagellaNOT may haveFOR evolved. SALE OR DISTRIBUTION KEY CONCEPT NOT FOR SALE OR DISTRIBUTION One additional type of flagellar organization 7. A glycocalyx protects against desiccation, attaches is found in the spirochetes, a group of gram- cells to surfaces, and helps pathogens evade the negative, coiled bacterial species. The cells are immune system. motile by flagella that extend from one or both © Jonespoles & Bartlett of the cell Learning, but fold back LLC along the cell body Many© bacterialJones &species Bartlett secrete Learning, an adhering LLC layer NOT FOR( FIGURE SALE 4.11 OR). Such DISTRIBUTION endo flagella lie in an area of ,NOT FOR SALE or polysaccharides OR DISTRIBUTION and small

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 110 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTInserting FOR aSALE capillary ORtube DISTRIBUTION NOT FOR SALE OR DISTRIBUTION with an attractant (orange dots) into a broth of motile “Biased random Inserting an empty bacterial cells produces a “Random walking” walking” capillary tube into a broth chemical gradient to of motile bacterial cells which the bacterial does not cause © Jones & Bartlett Learning, LLCcells are attracted © Jones & Bartlett Learning, LLC chemotaxis. (chemotaxis). Capillary NOTtube FOR SALE OR DISTRIBUTION CapillaryNOT tube FOR SALE OR DISTRIBUTION

No attractant Attractant Run Tumble © Jones & Bartlett Learning,Run LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Tumble

(A) (B) FIGURE 4.10 Chemotaxis. Chemotaxis represents a behavioral response to chemicals. (A) In a “,” rotation of the flagellum counter- © Jonesclockwise &causes Bartlett the bacterial Learning, cell to “ run,” LLC while rotation of the flagellum© clockwise Jones causes & Bartlett the bacterial Learning, cell to “tumble,” LLC as shown. (B) During NOTchemotaxis FOR (biasedSALE “random OR DISTRIBUTION walk”) to an attractant, such as , cellular behaviorNOT leads FOR to longerSALE runs OR and fewerDISTRIBUTION tumbles, which will result in biased movement toward the attractant. »» Predict the behavior of a bacterial cell if it sensed a repellant; that is a potential harmful or lethal chemical.

Endoflagella © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Outer membrane NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Peptidoglycan layer Endoflagella lie in This spirochete the periplasm. Cell membrane has a single Periplasm endoflagellum at each pole. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Endoflagella from the two poles overlap for © Jones & Bartlett Learning, LLC © Jones & Bartlettmuch Learning, of the cell length. LLC NOT(A) FOR SALE OR DISTRIBUTION (B) NOT FOR SALE OR DISTRIBUTION FIGURE 4.11 The Spirochete Endoflagella. (A) A light micrograph of Treponema pallidum shows the corkscrew-shaped spirochete cell. (Bar = 10 µm.) (B) Diagram showing the positioning of endoflagella in a spirochete. »» How are endoflagella different from true bacterial flagella?

proteins,© Jones called the& Bartlett glycocalyx Learning, (glyco = “sweet”; LLC calyx is to allow the ©cells Jones to attach & toBartlett surfaces. Learning, The LLC calyx NOT= “coat”). FOR The SALElayer can OR be thick DISTRIBUTION and covalently glycocalyx of V. choleraeNOT ,FOR for example, SALE ORpermits DISTRIBUTION bound to the cell, in which case it is known as a the cells to attach to the intestinal wall of the host. capsule. A thinner, loosely attached layer is referred The glycocalyx of pathogens therefore represents to as a slime layer. Colonies containing cells with a another virulence factor. Encapsulated:© Jones &glycocalyx Bartlett appear Learning, moist and LLC glistening. The actual ©Other Jones encapsulated & Bartlett Learning,pathogens, LLCsuch as Referring to a cell having capsule can be seen by light microscopy when (a principal cause of a capsule. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION observing cells in a preparation or ) and , evade : by transmission electron microscopy ( FIGURE 4.12 ). the immune system because they cannot be easily A process whereby cer- The glycocalyx serves as a buffer between the engulfed by white cells during phagocytosis. tain white blood cells cell and the external environment. Because of its Scientists believe the repulsion between bacterial © Jones() & Bartlett engulf Learning, LLC © Jones & Bartlett Learning, LLC foreign matter and often high water content, the glycocalyx can protect cells cell and is due to strong negative charges NOTdestroy FOR . SALE OR DISTRIBUTIONfrom desiccation. Another major role ofNOT the glyco- FOR SALEon the capsuleOR DISTRIBUTION and phagocyte surface.

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.4 External Cell Structures 111

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION4.3: Evolution NOT FOR SALE OR DISTRIBUTION The Origin of the Bacterial Flagellum

Flagella are an assembly of protein parts forming a rotary engine that, like an outboard motor, propel the cell forward through its moist environment. Recent work has shown how such a nanomachine may have evolved. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Several bacterial species,NOT including FOR SALE Yersinia ORpestis, DISTRIBUTION the agent of , contain structuresNOT to FOR SALE OR DISTRIBUTION inject toxins into an appropriate eukaryotic host cell. These bacterial cells have a hollow tube or needle to accomplish this process, just as the bacterial flagellum and filament are hollow (see diagram below). In addition, many of the flagellar proteins are similar to some of the injection proteins. In 2004, investigations discovered that Y. pestis cells actually contain all the needed for a flagellum— but the© Jones cells have & lost Bartlett the ability Learning, to use these LLC genes for that purpose. Y. pestis© Jonesis nonmotile & Bartlett and it Learning, LLC appearsNOT that FOR the cells SALE use a OR subset DISTRIBUTION of the flagellar proteins to build the injectionNOT device. FOR SALE OR DISTRIBUTION One scenario then is that an ancient cell evolved a structure that was the progenitor of the injection and flagellar systems. In fact, many of the proteins in the basal body of flagellar and injection systems are similar to proteins involved in proton ( ; H+) transport. Therefore, a proton transport system may have evolved into the injection device and, through diversification events, evolved into the © Jones &motility Bartlett structure Learning, present on LLC many bacterial cells today. © Jones & Bartlett Learning, LLC NOT FOR SALEThe fascinating OR DISTRIBUTION result of these investigations and proposalsNOT is FORit demonstrates SALE OR that DISTRIBUTIONstructures can evolve from other structures with a different function. It is not necessary that evolution “design” a structure from scratch but rather it can modify existing structures for other functions. Individuals have proposed that the complexity of structures like the bacterial flagellum are just too complex to arise gradually through a step-by-step process. However, the investigations being conducted illustrate that© Jonesa step-by-step & Bartlett evolution Learning, of a specific LLCstructure is not required. Rather,© thereJones & Bartlett Learning, LLC can be cooperation, whereNOT one FOR structure SALE is modified OR DISTRIBUTION to have other functions. The bacterial flagellumNOT FOR SALE OR DISTRIBUTION almost certainly falls into that category.

© Jones & OutsideBartlett of cell Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Hollow NOT FOR SALE OR DISTRIBUTION filament Hollow needle

Rotating © Jones & Bartlett Learning, LLC L ring © Joneshook & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALEOuter membr OR aneDISTRIBUTION Peptidoglycan P ring Rod Rod Basal body Cell membrane

© Jones & BartlettMS ring Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Protein export Cytosol system

A bacterial injection device (left) compared to a bacterial flagellum (right). © Jones &Both Bartlett have a protein Learning, export system LLC in the base of the basal body.© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 112 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Capsules

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Cell

© Jones & Bartlett Learning, LLC © JonesCapsule & Bartlett Learning, LLC NOT FOR(A) SALE OR DISTRIBUTION (B) NOT FOR SALE OR DISTRIBUTION FIGURE 4.12 The Bacterial Glycocalyx. (A) Demonstration of the presence of a capsule in an species by negative staining and observed by phase-contrast microscopy. (Bar = 10 µm.) (B) A false-color transmission electron micrograph of Escherichia coli. The cell is surrounded by a thick capsule (pink). (Bar = 0.5 µm.) »» How does the capsule provide protection for the bacterial cell? © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION A slime layer usually contains a mass of tan- on the tooth surface. TEXTBOOK CASE 4 gled fibers of a called (see (p. 113) details a medical consequence of a Chapter 2). The fibers attach the bacterial cell to biofilm. tissue© surfaces. Jones &A caseBartlett in point Learning, is Streptococcus LLC CONCEPT AND REASONING© Jones CHE &C BartlettKS Learning, LLC mutans,NOT an importantFOR SALE cause OR of toothDISTRIBUTION decay previ- 4.7 Under what circumstancesNOT FOR might SALE it be advantageous OR DISTRIBUTION ously discussed in MicroFocus 2.4. This species to a bacterial cell to have a capsule rather than a forms , which represents a type of slime layer?

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE4.5 ORThe DISTRIBUTION Cell Envelope NOT FOR SALE OR DISTRIBUTION The cell envelope is a complex structure that cell membrane. As described in Chapter 3, most forms the two “wrappers”—the cell wall and the microbes live in an environment where there cell membrane—surrounding the cell cytoplasm. are more dissolved materials inside the cell than © JonesHypertonic: & Bartlett Learning,The cell wallLLC is relatively porous to ©the Jones move- & outside.Bartlett This Learning, hypertonic LLC condition in the cell A solution with more ment of substances whereas the cell membrane means water diffuses inward, accounting for the NOTdissolved FOR SALEmaterial OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION (solutes) than the regulates transport of nutrients and metabolic increased osmotic pressure. Without a cell wall, surrounding solution. products. the cell would rupture or undergo osmotic ( FIGURE 4.13 ). It is similar to blowing so much The Bacterial Cell Wall Is a Tough air into a balloon that the air pressure bursts the and ©Pr Jonesotective & ExterBartlettnal Learning,Shell LLC balloon. © Jones & Bartlett Learning, LLC KEY NOTCONC EPTFOR SALE OR DISTRIBUTION The bacterial cellNOT wall FOR differs SALE markedly OR from DISTRIBUTION 8. Bacterial cell walls help maintain cell shape and pro- tect the cell membrane from rupture. the walls of archaeal cells and cells of eukaryotic microorganisms (algae and fungi) in containing The fact that most all bacterial and archaeal cells peptidoglycan, which is a network of disaccha- © Jones &have Bartlett a cell wallLearning, suggests LLC the critical role this ride© chainsJones (glycan & Bartlett strands) Learning, cross-linked byLLC short, NOT FORstructure SALE OR must DISTRIBUTION play. By covering the entire cell elasticNOT FOR (SALEFIGURE 4.14AOR DISTRIBUTION). Each disaccharide surface, the cell wall acts as an exoskeleton to unit in this very large molecule is composed of two protect the cell from injury and damage. It helps, alternating monosaccharides, N-acetylglucosamine along with the cytoskeleton (see Section 4.6), (NAG) and N-acetylmuramic acid (NAM) (see to maintain the shape of the cell and reinforce Chapter 2). The backbone can occur © Jones & Bartlett Learning,the cell envelope LLC against the high intracellular© Jones & inBartlett multiple Learning,layers connected LLC by side chains of four NOT FOR SALE OR DISTRIBUTIONwater (osmotic) pressure pushing againstNOT FOR the SALEamino acidsOR DISTRIBUTIONand cross-bridges.

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.5 The Cell Envelope 113

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE Textbook OR DISTRIBUTION CASE 4NOT FOR SALE OR DISTRIBUTION An Outbreak of cloacae Associated with a Biofilm

Hemodialysis is a treatment© Jones for people& Bartlett with severe Learning, chronic kidney LLC disease (kidney failure). The© Jones treat- & Bartlett Learning, LLC ment filters the patient’sNOT blood FOR to SALEremove wastesOR DISTRIBUTION and excess water. Before a patient begins NOThemo- FOR SALE OR DISTRIBUTION dialysis, an access site is created on the lower part of one arm. Similar to an intravenous (IV) site, a tiny tube runs from the arm to the dialysis machine. The patient’s blood is pumped through the dialysis machine, passed through a filter or artificial kidney called a dialyzer, and the cleaned blood returned to the patient’s body at the access site. The complete process can take 3 to 4 hours.

1© DuringJones September & Bartlett 1995, Learning,a patient at an LLC ambulatory hemodialysis center© Jonesin Montreal, & Bartlett Canada Learning, LLC NOTreceived FOR treatment SALE on OR a hemodialysis DISTRIBUTION machine to help relieve the effectsNOT of kidneyFOR disease.SALE TheOR DISTRIBUTION treatment was performed without incident.

2 The next day, a second patient received treatment on the same hemodialysis machine. His treat- ment also went normally, and he returned to his usual activities after the session was completed. © Jones & Bartlett3 In the Learning,following days, LLC both patients experienced bloodstream© Jones infections & Bartlett (BSIs). Learning, They had high LLC NOT FOR SALEfever, OR muscular DISTRIBUTION aches and pains, sore throat, and impairedNOT FOR blood circulation.SALE OR Because DISTRIBUTION the symp- toms were severe, the patients were hospitalized. The clinical microbiology lab reported that both patients had infections of Entero bacter cloacae, a gram-negative rod. Textbook CASE 4 In the following months, an epidemiological investigation reviewed other hemodialysis patients at that center. In all, seven additional adult patients were identified who had used the same hemodialysis machine.© Jones They &discovered Bartlett all Learning, seven had similar LLC BSIs. © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 5 Inspection of the hemodialysis machine used by these nine patients indicated the presence of biofilms containing , which was identical to those samples taken from the © patients’Jones bloodstreams& Bartlett (see Learning, figure). LLC © Jones & Bartlett Learning, LLC 6NOT Further FOR study SALE indicated OR that DISTRIBUTION the dialysis NOT FOR SALE OR DISTRIBUTION machine was contaminated with E. cloacae, specifically where fluid flows.

7 It was discovered that hospital personnel were dis infecting the machines correctly. The prob- © Jones & Bartlettlem was Learning, that the valves LLC in the drain line were © Jones & Bartlett Learning, LLC NOT FOR SALEmalfunctioning, OR DISTRIBUTION allowing a backflow of con- NOT FOR SALE OR DISTRIBUTION taminated material.

8 Health officials began a hospital education Similar to the description in this textbook case, bio- program to ensure that further outbreaks of films consisting of Staphylococcus cells can contami- would© be Jones minimized. & Bartlett Learning,nate hemodialysis LLC machines (Bar = 5 µm.).© Jones & Bartlett Learning, LLC Questions: NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION (Answers can be found on the Student Companion Website in D.)

A. Suggest how the hemodialysis machine originally became contaminated. B. Why weren’t the other five cases of BSI correlated with the hemodialysis machine until the epi- © demiologicalJones & Bartlett investigation Learning, was begun? LLC © Jones & Bartlett Learning, LLC C.NOT How FOR could futureSALE outbreaks OR DISTRIBUTION of infection be prevented? NOT FOR SALE OR DISTRIBUTION For additional information see www.cdc.gov/mmwr/preview/mmwrhtml/00051244.htm.

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 114 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTAutolytic FOR SALEenzyme: OR DISTRIBUTION NOT FOR SALEon the cellOR wall, DISTRIBUTION controlling the activity of auto- An that breaks lytic acting on the peptidoglycan, and/or bonds in the peptido- glycan, thereby causing acting as a virulence factor that triggers fever and lysis of the cell (e.g., . ). The actinomycetes are phylogenetically © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC related to the gram-positive bacteria. However, NOT FOR SALE OR DISTRIBUTION these bacterial cellsNOT have evolvedFOR SALE another OR type DISTRIBUTION of wall architecture to protect the cell membrane from rupture. In organisms like Mycobacterium, the cell wall is composed of a waxy called © Jones & Bartlett Learning, LLC mycolic© Jones acid &that Bartlett is arranged Learning, in two layers LLC that NOT FOR SALE OR DISTRIBUTION areNOT covalently FOR attached SALE ORto the DISTRIBUTION underlying pepti- doglycan. Such a hydrophobic layer is impervi- ous to the Gram stains, so stain identification of M. tuberculosis is carried out using the acid-fast stain procedure (see Chapter 3). © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Gram-Negative Walls. The cell wall of NOT FOR SALE OR DISTRIBUTION NOT FOR SALEgram-negative OR DISTRIBUTION bacterial cells is structurally quite different from that of the gram-positive wall ( FIGURE 4.14C ). The peptidoglycan layer is two- dimensional; the glycan strands compose just a © Jones & Bartlett Learning, LLC single layer or two. ©This Jones is one reason& Bartlett why it Learning,loses LLC FIGURENOT 4.13 FOR Cell Rupture SALE (Lysis). OR DISTRIBUTIONA false-color elec- the violet dyeNOT during FOR the GramSALE stain. OR Also, DISTRIBUTION tron micrograph showing the lysis of a Staphylococcus there is no present. aureus cell. The addition of the antibiotic inter- feres with the construction of the peptidoglycan in new The unique feature of the gram-negative cell cells, and they quickly burst (top cell). (Bar = 0.25 µm.) wall is the presence of an outer membrane, which »» Where is the concentration of dissolved substances is separated by a gap, called the periplasm, from © Jones &(solutes) Bartlett higher, Learning, inside the cell LLCor outside? Explain how © Jones & Bartlett Learning, LLC this leads to cell lysis. the cell membrane. This gel-like compartment NOT FOR SALE OR DISTRIBUTION containsNOT FORdigestive SALE enzymes OR DISTRIBUTIONand transport pro- teins to speed entry of nutrients into the cell. The peptidoglycan layer is located in the periplasm There is more to a bacterial cell wall than just and attached to in the cell membrane. peptidoglycan, so several forms of cell wall archi- © Jones & Bartlett Learning, LLC © Jones & BartlettThe inner Learning, half of the LLC outer membrane con- tecture exist. NOT FOR SALE OR DISTRIBUTION NOT FOR SALEtains OR DISTRIBUTION similar to the cell membrane. Gram-Positive Walls. Most gram-positive However, the outer half is composed primarily of bacterial cells have a very thick, rigid peptidogly- (LPS), which consists of poly- can cell wall ( FIGURE 4.14B ). The and saccharide attached to a unique anchoring lipid thickness (25 nm) of this material may be one molecule known as lipid A. The so-called O poly- Endotoxin: reason© whyJones they & retain Bartlett the crystal Learning, violet LLCin the saccharide is used to© identify Jones variants & Bartlett of a species Learning, LLC A that can acti- vate inflammatory re- GramNOT stain FOR(see Chapter SALE 3).OR The DISTRIBUTION multiple layers (e.g., strain O157:H7NOT of E. coliFOR). On SALE cell , OR lipid DISTRIBUTION sponses, leading to high of glycan strands are cross-linked to one another A is released and represents an endotoxin that can fever, shock, and organ both in the same layer as well as between layers be toxic if ingested (Chapter 13). failure. forming a three-dimensional mesh. The outer membrane also contains unique pro- Hydrophilic: © Jones & BartlettThe gram-positive Learning, cell LLC wall also contains a teins© calledJones porins & Bartlett. These proteins Learning, form pores LLC in the Pertaining toNOT molecules FOR sugar- SALE OR polymerDISTRIBUTION called teichoic acid. Wall outerNOT membrane FOR SALE through OR which DISTRIBUTION small, hydrophilic or parts of molecules teichoic , which are bound to the glycan chains that are soluble in water. molecules (, amino acids, some ions) diffuse or to the cell membrane, are essential for cell via- passively into the periplasm. The outer membrane Hydrophobic: bility—if the genes for teichoic acid synthesis are also contains substrate-specific active transporters Pertaining to molecules deleted, cell death occurs. Still, the function of the for some needed compounds, such as vitamins. © Jonesor parts & o f Bartlettmolecules Learning, LLC © Jones & Bartlett Learning, LLC that are not soluble in teichoic acids remains unclear. They may protect However, other larger, hydrophobic molecules NOTwater. FOR SALE OR DISTRIBUTIONthe cell envelope by establishing a surfaceNOT charge FOR SALEcannot pass,OR DISTRIBUTIONpartly accounting for the resistance of

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.5 The Cell Envelope 115

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION -acetylglucosamineNOT FOR (NAG)SALE OR DISTRIBUTIONside chain -acetylmuramic acid (NAM) Peptide cross-bridge

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Carbohydrate NOT FOR SALE OR DISTRIBUTION NOT FOR SALE"backbone" OR DISTRIBUTION

Gram-positive bacterial cell (A) Structure of peptidoglycan

© Jones & Bartlett Learning,Teichoic LLC acid © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Cell wall

Cell envelope

Cell membrane © Jones & Bartlett Learning,Phospholipids LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Protein

Cytoplasm © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR(B) Gram-positiveDISTRIBUTION cell wall NOT FOR SALE OR DISTRIBUTION

Porins O polysaccharide Lipopolysaccharide (LPS) © Jones & Bartlett Learning, LLC © JonesLipid & A Bartlett Learning, LLC NOT FORGram-negative SALE OR bacterial DISTRIBUTION cell NOT FOR SALE OR DISTRIBUTION

Outer membrane Cell wall

Peptidoglycan Cell envelope © Jones & Bartlett Learning, LLC © Jones & Bartlett PeriplasmLearning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Cell membrane

Lipoprotein © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Cytoplasm

(C) Gram-negative cell wall

FIGURE 4.14 A Comparison of the Cell Walls of Gram-Positive and Gram-Negative Bacterial Cells. (A) The structure of peptidoglycan is shown as© unitsJones of NAG & and Bartlett NAM joined Learning, laterally by amino LLC acid cross-bridges and vertically© Jonesby side chains & Bartlett of four amino Learning, acids. (B) The LLC cell wall of a gram-positiveNOT bacterialFOR SALE cell is composed OR DISTRIBUTION of multiple peptidoglycan layers combined withNOT teichoic FOR acid SALEmolecules. OR (C) InDISTRIBUTION the gram-negative cell wall, the peptidoglycan layer is much thinner, and there is no teichoic acid. Moreover, an outer membrane overlies the peptidoglycan layer such that both comprise the cell wall. Note the structure of the outer membrane in this figure. It contains proteins and the outer half is unique in containing lipopolysaccharide. »» Simply based on cell wall structure, assess the potential of gram-positive and gram-negative cells as pathogens.

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 116 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONTABLE NOT FOR SALE OR DISTRIBUTION 4.2 A Comparison of Gram-Positive and Gram-Negative Cell Walls Characteristic Gram Positive Gram Positive Acid-fast Gram Negative Peptidoglycan Yes, thick layer Yes Yes, thin layer © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Teichoic acids Yes No1 No OuterNOT membrane FOR SALE OR DISTRIBUTION No Yes NOT FOR Yes SALE OR DISTRIBUTION No Yes No (LPS) No No Yes Porin proteins No Yes Yes © Jones & BartlettPeriplasm Learning, LLC No Yes© Jones & Bartlett Learning, Yes LLC NOT FOR SALE1 Have a ORdifferent DISTRIBUTION type of glycopolymer. NOT FOR SALE OR DISTRIBUTION

gram-negative cells to many antimicrobial agents, that self-assemble into a crystalline lattice 5 nm to © Jones & Bartlett Learning,dyes, , LLC and lysozyme. © Jones & 25Bartlett nm thick. Learning, LLC Before leaving the bacterial cell walls, a brief Although the walls may be structurally differ- NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION mention should be made of bacterial species that ent and the molecules form a different structural lack a cell wall. The are a wall-less pattern, the function is the same as in bacterial genus that is again phylogenetically related to the species—to provide mechanical support and pre- gram-positive bacteria. Taxonomists believe that vent osmotic lysis.

the mycoplasmas© Jones & once Bartlett had a Learning,cell wall but LLClost it CONCEPT AND REASONING© Jones CHECKS & Bartlett Learning, LLC becauseNOT of theirFOR parasitic SALE relationshipOR DISTRIBUTION with their 4.9 Distinguish betweenNOT peptidoglycan FOR SALE and OR pseu do- DISTRIBUTION host. To help protect the cell membrane from rup- peptidoglycan cell walls. ture, the mycoplasmas are unusual in containing Glycolipid: large amounts of glycolipid in the cell membrane. A molecule consisting of TABLE 4.2 summarizes the major differences The Cell Membrane Represents a polysaccharid©e link Jonesed to & Bartlett Learning, LLC Selective© Jones Barrier & Bartlett Between Learning, the Cell LLC lipid. between the three major types of bacterial cell NOT FORwalls. SALE OR DISTRIBUTION EnvironmentNOT FOR SALEand the OR Cell DISTRIBUTION Cytoplasm KEY CONCEPT CONCEPT AND REASONING CHECKS 10. Molecules and ions cross the cell membrane by facili- 4.8. Penicillin and lysozyme primarily affect peptido- tated diffusion or active transport. glycan synthesis in gram-positive bacterial cells. © Jones & Bartlett Learning,Why areLLC these agents less effective against© Jones gram- & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONnegative bacterial cells? NOT FOR SALEA cell OR(or plasmaDISTRIBUTION) membrane is a universal structure that separates external from internal (cytoplasmic) environments, preventing soluble The Archaeal Cell Wall Also Provides materials from simply diffusing into and out of Mechanical Strength the cell. One exception is water, which due to its KEY ©CONCEPT Jones & Bartlett Learning, LLC small size and overall© Joneslack of charge& Bartlett can diffuse Learning, LLC 9. ArchaealNOT FOR cell walls SALE have crystalline OR DISTRIBUTION layers. slowly across the membrane.NOT FOR SALE OR DISTRIBUTION The bacterial cell membrane, which is about Archaeal species vary in the type of wall they 7 nm thick, is 25% (by weight) and possess. None have the peptidoglycan typical 75% protein. In illustrations, the cell membrane © Jones &of Bartlettthe Bacteria. Learning, Some species LLC have a pseudo- appears© Jones very rigid & Bartlett ( FIGURE 4.15 Learning,). In reality, LLCit is quite NOT FORpeptido SALE glycanOR DISTRIBUTION where the NAM is replaced by fluid,NOT having FOR the SALEconsistency OR of DISTRIBUTION oil. This means N-acetyltalo samine uronic acid (NAT). Other the mosaic of phospholipids and proteins are not archaeal cells have walls made of polysaccharide, cemented in place, but rather they can move laterally protein, or both. in the membrane. This dynamic model of membrane The most common cell wall among archaeal structure therefore is called the . © Jones & Bartlett Learning,species is aLLC surface layer called the S-layer© Jones. It con- & BartlettThe phospholipid Learning, molecules, LLC typical of most NOT FOR SALE OR DISTRIBUTIONsists of hexagonal patterns of protein or glycoproteinNOT FOR SALEbiological OR membranes, DISTRIBUTION are arranged in two parallel

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.5 The Cell Envelope 117

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORlayers SALE (a bilayer) OR DISTRIBUTION and represent the barrier func- NOT FOR SALE OR DISTRIBUTION tion of the membrane. The phospholipids contain Outside of cell a charged head group attached to two Integral Hydrophilic hydrophobic chains (see Chapter 2). The membrane protein fatty acid “tails” are the portion that forms the permeability barrier. In© contrast, Jones the & Bartletthydrophilic Learning, LLC © Jones & Bartlett Learning, LLC head groups are exposedNOT to the FOR aqueous SALE external OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION or cytoplasmic environments. Several antimicrobial substances act on the membrane bilayer. The antibiotic polymyxin pokes ©holes Jones in the & bilayer, Bartlett while Learning, some LLC © Jones & Bartlett Learning, LLC and alcoholsNOT FOR dissolve SALE the ORbilayer. DISTRIBUTION Such action Hydrophobic NOT FOR SALE OR DISTRIBUTION allows the cytoplasmic contents to leak out of Phospholipid bacterial cells, resulting in death through cell lysis. Cytoplasm Bilayer (7 nm)

A diverse population of membrane proteins FIGURE 4.15 The Structure of the Bacterial Cell Membrane. The cell membrane of a populates the phospholipid bilayer. These mem- bacterial cell consists of a phospholipid bilayer in which are embedded integral mem- © Jonesbrane & Bartlett proteins oftenLearning, have stretches LLC of hydrophobic brane© proteins. Jones Other & proteinsBartlett and Learning,ions may be associated LLC with the integral proteins NOT FOR SALE OR DISTRIBUTION or theNOT phospholipid FOR heads.SALE »» WhORy is DISTRIBUTION the cell membrane referred to as a fluid mosaic amino acids that interact with the hydrophobic structure? fatty acid chains in the membrane. These proteins span the width of the bilayer and are referred to High as “integral membrane proteins.” Other proteins, Outside of cell called “peripheral membrane proteins,” are associ- Solute © Jones & Bartlett Learning, LLC molecule © Jones & Bartlett Learning, LLC ated with the polar heads of the bilayer or exposed NOT FOR SALE OR DISTRIBUTIONCell Binding NOT FOR SALE OR DISTRIBUTION parts of integral membrane proteins. membrane site Bacterial and archaeal cell membrane pro- teins carry out numerous important functions, some of which are absent from the eukaryotic plasma© membrane. Jones & This Bartlett includes Learning, enzymes needed LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION for cell wall synthesis and energy metabolism. Transport As mentioned, bacterial and archaeal cells lack Solute Concentration Gradient protein mitochondria and part of that ’s func- Cytoplasm tion is carried out by the cell membrane. Other Low © Jonesmembrane & Bartlett proteins Learning, help anchor LLC the DNA to the FIGURE© Jones4.16 Facilitated & Bartlett Transport Learning, Through a Membrane LLC Protein. Many transport membrane during replication or act as receptors proteins facilitate the diffusion of nutrients across the . The transport protein NOT FOR SALE OR DISTRIBUTION formsNOT a hydrophilic FOR channel SALE through OR whichDISTRIBUTION a specific solute can diffuse. »» Why would a of chemical information, sensing changes in envi- solute move through a membrane protein rather than simply across the lipid bilayer? ronment conditions and triggering appropriate behavioral responses as demonstrated through quorum sensing. their concentration gradient; that is, from an area Perhaps the largest© group Jones of integral& Bartlett mem- Learning,of higher LLC concentration to one of lower© Jones concen- & Bartlett Learning, LLC brane proteins is involvedNOT FORas transporters SALE OR of DISTRIBUTIONtration ( FIGURE 4.16 ). By acting as a NOTconduit FOR for SALE OR DISTRIBUTION charged solutes, such as amino acids, simple sug- diffusion or as a transporter through the hydro- ars, nitrogenous bases, and ions across the lipid phobic bilayer, hydrophilic solutes can enter or bilayer. The transport proteins are highly specific leave without the need for cellular energy. though,© onlyJones transporting & Bartlett a single Learning, molecular LLC spe- Unlike facilitated© diffusion, Jones &active Bartlett transport Learning, LLC cies orNOT a very FORsimilar SALE class of ORmolecules. DISTRIBUTION Therefore, allows different concentrationsNOT FOR ofSALE solutes OR to DISTRIBUTIONbe there are many different transport proteins to reg- established outside or inside of the cell against the ulate the diverse molecular traffic that must flow concentration gradient. These membrane proteins into or out of a cell. act as “pumps” and, as such, demand an energy The transport process can be passive or active. input from the cell. Cellular processes such as © JonesIn & facilitated Bartlett diffusionLearning,, integral LLC membrane pro- cell ©energy Jones production & Bartlett and flagellaLearning, rotation LLC also NOT FORteins SALE facilitate OR the DISTRIBUTION movement of materials down dependNOT on FOR active SALEtransport. OR DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 118 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONCONCEPT AND REASONING CHECKS NOT FOR SALEthe Archaea. OR DISTRIBUTION The tails are bound to the 4.10 Justify the necessity for phospholipids and proteins by “ether linkages” rather than the “ester link- in the cell membrane. ages” found in the domains Bacteria and Eukarya ( FIGURE 4.17A ). The Archaeal Cell Membrane Also, typical fatty acid tails are absent from Differs© Jones from Bacterial& Bartlett Learning, LLC the membranes; instead,© Jones repeating & Bartlett five-carbon Learning, LLC and NOTEukaryal FOR Membranes SALE OR DISTRIBUTION units are linked end-to-endNOT FOR to SALEform lipid OR tailsDISTRIBUTION KEY CONCEPT longer than the fatty acid tails. The result can be 11. Archaeal membranes are structurally unique. a lipid bilayer or monolayer ( FIGURE 4.17B ). A monolayer provides an advantage to the hyper- Besides the differences in sequences for ribo- © Jones & Bartlett Learning, LLC © Jones by & preventingBartlett aLearning, peeling in two LLC of the somal RNA in the domain Archaea, another major NOT FOR SALE OR DISTRIBUTION membrane,NOT FOR which SALE would occurOR DISTRIBUTION with a typical bilayer difference used to separate the archaeal organisms structure under high temperature conditions. into their own domain is the chemical nature of the cell membrane. The manner in which the hydrophobic lipid CONCEPT AND REASONING CHECKS © Jones & Bartlett Learning,tails are attachedLLC to the glycerol is different© Jones in & Bartlett4.11 What isLearning, unique about archaeal LLC membrane structure? NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Head group

Bacterial/Eukaryal Archaeal Glycerol © Jonesmembranes & BartlettO Learning, LLC membranes O © Jones & Bartlett Learning, LLC

NOT FORH2C SALECH CH 2OR DISTRIBUTION H2C CH CH2NOT FOR SALE OR DISTRIBUTION

O O O O Ester Ether O CCO linkage linkage CC © Jones &(A) Bartlett Learning,RR LLC Tails © JonesR' R' & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION OO OO OO OO OO OO O O O O

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Extracellular NOT FOR SALE OR DISTRIBUTION fluid NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALECytoplasm OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Phospholipid bilayer— Phospholipid monolayer—

Bacteria, Eukarya, some extremely thermophilic

O O O

O Archaea OO OO OO most Archaea OO

OO © Jones & Bartlett Learning, LLC OO © Jones & Bartlett Learning, LLC

NOT FOR SALEBilayers OR DISTRIBUTION NOT FOR SALEMonolayers OR DISTRIBUTION

(B) Bilayers

FIGURE 4.17 Structure of Cell Membranes. (A) Bacterial and eukaryal cell membranes involve an ester linkage join- ing the glycerol to the fatty acid tails (R) while archaeal membranes have an ether linkage to the isoprenoid tails (RЈ). © Jones & Bartlett Learning,(B) Bacterial LLC and eukaryal membranes form a ©bilayer Jones while archaeal& Bartlett membranes Learning, may be a bilayer LLC or a monolayer. »» What NOT FOR SALE OR DISTRIBUTIONidentifies an ester linkage from an ether linkage?NOT FOR SALE OR DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.6 The Cell Cytoplasm and Internal Structures 119

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR4.6 SALEThe OR CellDISTRIBUTION Cytoplasm and Internal StructuresNOT FOR SALE OR DISTRIBUTION The cell membrane encloses the cytoplasm, which reproduction. Because most cells only have one is the compartment within which most growth and chromosome, the cells are genetically haploid. Haploid: Unlike eukaryotic microorganisms and other Having a single set of metabolism occurs. The cytoplasm consists of the genetic information. cytosol, a semifluid mass© ofJones proteins, & aminoBartlett acids, Learning, , LLC the nucleoid and chromosome© Jones do & Bartlett Learning, LLC sugars, , ,NOT vitamins, FOR andSALE ions—all OR DISTRIBUTION not undergo and having but NOTthe one FOR set SALE OR DISTRIBUTION dissolved in water (see Chapter 2)—and several of genetic information cannot undergo . bacterial structures or subcompartments, each The complete set of genes in an organism with a specific function. or is called the . For example, the © Jones & Bartlett Learning, LLC genome of E. coli, a typical© Jones bacterial & Bartlett species in Learning,the LLC The NucleoidNOT FOR Represents SALE OR DISTRIBUTIONmid-size range, containsNOT about FOR 4,300 SALE genes. OR In allDISTRIBUTION a Subcompartment Containing cases, these genes determine what proteins and the Chromosome enzymes the cell can make; that is, what meta- KEY CONCEPT bolic reactions and activities can be carried out. 12. The nucleoid contains the cell’s essential genetic For E. coli, this equates to some 2,000 different © Jones & Bartlett information. Learning, LLC proteins.© Jones Extensive & Bartlett coverage Learning, of bacterial DNALLC is NOT FOR SALE OR DISTRIBUTION presentedNOT inFOR Chapter SALE 8. OR DISTRIBUTION The chromosome region in bacterial and archaeal CONCEPT AND REASONING CHECKS cells appears as a diffuse mass termed the nucle- 4.12 Why do we say that the bacterial chromosome contains oid ( FIGURE 4.18 ). The nucleoid is not surrounded the “essential hereditary information”? by a membrane envelope;© Jones rather, &it representsBartlett Learning,a LLC © Jones & Bartlett Learning, LLC subcompartment in the cytoplasm where the DNA NOT FOR SALE OR DISTRIBUTIONPlasmids Are Found in Many BacterialNOT FOR SALE OR DISTRIBUTION aggregates and ribosomes are absent. Usually there and Archaeal Cells is a single chromosome per cell and, with few KEY CONCEPT exceptions, exists as a closed loop of DNA and 13. Plasmids contain nonessential genetic information. protein. The© DNAJones contains & Bartlett the essential Learning, hereditary LLC © Jones & Bartlett Learning, LLC informationNOT FORfor cell SALE growth, OR metabolism, DISTRIBUTION and Besides a nucleoid, manyNOT bacterialFOR SALE and archaeal OR DISTRIBUTION cells also contain smaller molecules of DNA called plasmids. About a tenth the size of the chro- mosome, these stable, extrachromosomal DNA molecules exist as closed loops containing 5 to © Jones & Bartlett Learning, LLC 100 ©genes. Jones There & Bartlettcan be one Learning, or more plasmids LLC NOT FOR SALE OR DISTRIBUTION in a NOTcell and FOR these SALE may contain OR DISTRIBUTION similar or differ- ent genes. Plasmids replicate independently of the chromosome and can be transferred between cells during recombination. They also represent impor- © Jones & Bartlett Learning,tant vectors LLC in industrial technologies© Jonesthat use & BartlettVector: Learning, LLC . Both topics are covered in A genetic element ca- NOT FOR SALE OR DISTRIBUTION NOT FOR SALEpable o fOR incorporating DISTRIBUTION Chapter 9. and transferring genetic Although plasmids may not be essential for information. cellular growth, they provide a level of genetic flexibility. For example, some plasmids possess © Jones & Bartlett Learning, LLC genes for disease-causing© Jones toxins & and Bartlett many carry Learning, LLC NOT FOR SALE OR DISTRIBUTIONgenes for chemical orNOT antibiotic FOR SALEresistance. OR For DISTRIBUTION FIGURE 4.18 The Bacterial Nucleoid. In this false- this latter reason, these genetic elements often are color transmission electron micrograph of Escherichia coli, (orange) occupy a large area in a bacterial cell. called R plasmids (R for resistance).

Both longitudinal (center cells) and cross sections (cell CONCEPT AND REASONING CHECKS »» © Jonesupper & Bartlett right) of E. Learning,coli are visable. LLC (Bar = 0.5 µm.) How 4.13© What Jones properties & Bartlett distinguish Learning, the bacterial chromo-LLC does a nucleoid differ from the eukaryotic cell nucleus some from a plasmid? NOT FORdescribed SALE in theOR previous DISTRIBUTION chapter? NOT FOR SALE OR DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 120 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONOther Subcompartments Exist NOT FOR SALEThe OR free DISTRIBUTIONribosomes make soluble proteins that in the Cell Cytoplasm are used in the cell, while the membrane-attached KEY CONCEPT ones produce proteins for the cell envelope and 14. Ribosomes, microcompartments, and inclusions carry for secretion. out specific intracellular functions. Microcompartments. Recently, some © Jones & Bartlett Learning, LLC bacterial species have© Jones been found& Bartlett to contain Learning, LLC For aNOT long timeFOR the SALE cytoplasm OR DISTRIBUTION was looked at as microcompartmentsNOT. The FOR microcompartments SALE OR DISTRIBUTION a bag enclosing the genetic machinery and bio- appear to be unique to the Bacteria and consist chemical reactions. As more studies were carried of a polyprotein shell 100–200 nm in diameter out with the and with bio- ( FIGURE 4.20 ). In the cyanobacteria, microcom- © Jones &chemical Bartlett techniques, Learning, it became LLC evident that the partments© Jones called & Bartlett “carboxysomes” Learning, function LLC to NOT FORcytoplasm SALE OR contained DISTRIBUTION “more than meets the eye.” enhanceNOT carbonFOR SALEdioxide fixationOR DISTRIBUTION and in some non- Ribosomes. One of the universal cell struc- photosynthetic species, microcompartments limit tures mentioned in Chapter 3 was the ribosome. diffusion of volatile or toxic metabolic products. There are thousands of these nearly spherical par- In general, microcompartments represent local- ticles in the cell cytoplasm, which gives it a gran- ized areas where enzymes can more directly inter- © Jones & Bartlett Learning,ular appearance LLC when viewed with the© Joneselectron & actBartlett with their Learning, substrates LLC or potentially sequester NOT FOR SALE OR DISTRIBUTIONmicroscope ( FIGURE 4.19A ). In addition,NOT there FOR also SALEharmful OR reaction DISTRIBUTION products. are ribosomes loosely attached to the cell mem- Inclusions. Cytoplasmic structures, called brane. Their relative size is measured by how fast inclusions, can be found in the cytoplasm. Many Centrifuge: they settle when spun in a centrifuge. Measured of these bodies store nutrients or the monomers An instrument that spins in Svedberg units (S), bacterial and archaeal ribo- for cellular structures. For example, some inclu- suspended in © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC liquid at high speed. somesNOT represent FOR 70S SALE particles. OR DISTRIBUTION sions function as nutrientNOT FOR reserves. SALE They OR con- DISTRIBUTION The ribosomes are built from RNA and protein sist of aggregates or granules of polysaccharides and are composed of a small subunit (30S) and a (), globules of elemental , or lipid. large subunit (50S) ( FIGURE 4.19B ). For proteins Other inclusions can serve as important iden- to be synthesized, the two subunits come together tification characters for bacterial pathogens. © Jones &to Bartlettform a 70S Learning, functional ribosomeLLC (Chapter 8). One© exampleJones & is Bartlettthe diphtheria Learning, bacilli that LLC con- NOT FORSome SALE antibiotics, OR DISTRIBUTION such as streptomycin and tetra- tainNOT metachromatic FOR SALE granules OR DISTRIBUTION, also called volutin cycline, prevent bacterial and archaeal ribosomes granules, which are deposits of polyphosphate from carrying out protein synthesis. (long chains of inorganic phosphate) along with

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTIONSubunits 70S Ribosome 50S © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC

NOT FOR SALE OR DISTRIBUTION NOTThe FOR 50S subunitSALE contains OR DISTRIBUTIONa 23S rRNA, 5S rRNA, and 34 proteins. + © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC The 70S bacterial ribosome (A) NOT FOR SALE OR DISTRIBUTION consists of a 50SNOT and 30S FOR SALE OR DISTRIBUTION30S subunit. (B) The 30S subunit contains a 16S rRNA and 21 proteins. © Jones & Bartlett Learning,FIGURE 4.19 LLCThe Bacterial Ribosome. (A) A© false-color Jones electron& Bartlett microscope Learning, image of Neisseria LLC gonorrhoeae, showing the nucleoid (yellow) and ribosomes (blue). (Bar = 1 µm.) (B) The functional 70S ribosome is assembled from a small NOT FOR SALE OR DISTRIBUTION(30S) and large (50S) subunit. »» How many rRNANOT molecules FOR andSALE proteins OR construct DISTRIBUTION a 70S ribosome?

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.6 The Cell Cytoplasm and Internal Structures 121

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION UntilNOT recently, FOR the SALE dogma OR was DISTRIBUTION that bacterial and archaeal cells lacked a cytoskeleton, which is a common feature in eukaryotic cells (see Chapter 3). However, it is now clear that cytoskeletal proteins that resemble those in the eukaryotic cytoskeleton © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC are present in bacterial and archaeal cells. NOT FOR SALE OR DISTRIBUTIONThe first protein discovered wasNOT a homolog FOR SALEHomolog: OR DISTRIBUTION of the eukaryotic protein , which forms An entity with similar attributes due to shared filaments that assemble into microtubules. The ancestry. homolog forms filaments similar to those in micro- © Jones & Bartlett Learning, LLC tubules but the filaments© Jones do not & assembleBartlett intoLearning, LLC NOT FOR SALE OR DISTRIBUTIONmicrotubules. TheseNOT tubulin-like FOR SALE proteins OR have DISTRIBUTION been found in all bacterial and archaeal cells examined and appear to function in the regula- tion of cell division. During this process, the pro- tein localizes around the neck of the dividing cell © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC where it recruits other proteins needed for the NOT FOR SALE OR DISTRIBUTION depositionNOT FORof a new SALE cell wall OR between DISTRIBUTION the dividing cells (MICRO FOCUS 4.5).

FIGURE 4.20 Microcompartments. Purified bacterial Protein homologs remarkably similar in three- microcompartments from are composed dimensional structure to eukaryotic microfilaments of a complex protein shell that© encasesJones metabolic & Bartlett enzymes. Learning, assemble LLC into filaments that help determine© Jones cell & Bartlett Learning, LLC (Bar ϭ 100 nm.) »» How do these bacterial microcompart- ments differ structurally fromNOT a eukaryotic FOR organelle? SALE OR DISTRIBUTIONshape in E. coli and . TheseNOT homo- FOR SALE OR DISTRIBUTION logs have been found in most nonspherical cells where they form a helical network beneath the calcium and other ions. These granules stain with cell membrane to guide the proteins involved in cell wall formation ( FIGURE 4.21A ). The homologs dyes such© Jones as methylene & Bartlett blue. SimilarLearning, LLC © Jones & Bartlett Learning, LLC also are involved with chromosome segregation called NOT“acidocalcisomes” FOR SALE are OR found DISTRIBUTION in the . NOT FOR SALE OR DISTRIBUTION Some aquatic and marine forms achieve during cell division and formation. buoyancy using gas , cytoplasmic com- Intermediate filaments (IF), another com- partments built from a water-tight protein shell. ponent of the eukaryotic cytoskeleton in some metazoans Metazoan: These vacuoles are filled with a gas to decrease the , have a homolog as well. The protein, called , helps determine the character- A member of the verte- © Jonesdensity & Bartlett of the cell,Learning, which generates LLC and regulates © Jones & Bartlett Learning, LLC brates, , and NOT FORtheir SALE buoyancy. OR DISTRIBUTION istic NOTcrescent FOR shape SALE of OR DISTRIBUTION crescentus cells. mollusks. The magnetosome, another type of inclusion or In older cells that become filamentous, crescentin maintains the helical shape of the cells by aligning subcompartment, is described in MICROFOCUS 4.4. with the inner cell curvature beneath the cytoplas- These inclusions, found in some aquatic bacterial mic membrane ( FIGURE 4.21B ). species, are invaginations of the cell membrane, © Jones & Bartlett Learning,Even LLC though the evolutionary relationships© Jones & Bartlett Learning, LLC which are coordinated and positioned by cytoskel- NOT FOR SALE OR DISTRIBUTIONare quite distant between bacterial/archaealNOT FOR and SALE OR DISTRIBUTION etal filaments similar to eukaryotic microfilaments. eukaryotic cytoskeletal proteins based on pro- tein sequence data, the similarity of their three- CONCEPT AND REASONING CHECKS 4.14 Provide the roles for the subcompartments found in dimensional structure and function is strong bacterial© Jones cells. & Bartlett Learning, LLC evidence supporting© homologous Jones & Bartlettcytoskeletons. Learning, LLC NOT FOR SALE OR DISTRIBUTION TABLE 4.3 summarizesNOT the FOR structural SALE features OR DISTRIBUTIONof bacterial and archaeal cells. Many Bacterial/Archaeal Cells Have

a “Cytoskeleton” CONCEPT AND REASONING CHECKS KEY CONCEPT 4.15 Evaluate the relationship between the eukaryotic © Jones 15.& BartlettCytoskeletal Learning, proteins regulate LLC cell division and help ©cytoskeleton Jones & and Bartlett the cytoskeletal Learning, protein homologs LLC NOT FOR SALEdetermine OR cell DISTRIBUTION shape. NOTin bacterial FOR and SALE archaeal OR cells. DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 122 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION 4.4: EnvironmentalNOT FOR MicrobiologySALE OR DISTRIBUTION Magnetic Navigation

To get from place to place, humans often require the assistance of maps, GPS systems, or gas station attendants. In the microbial world, life is generally more simple, and traveling is no exception. ©In Jonesthe early &1980s, Bartlett Richard Learning, P. Blakemore LLCand his colleagues at the University© Jones of New &Hampshire Bartlett Learning, LLC observedNOT mud-dwellingFOR SALE bacterial OR DISTRIBUTION cells gathering at the north end of water droplets.NOT FOR On further SALE study, OR DISTRIBUTION they discovered each cell had a chain of aligned magnetic particles acting like a compass directing the organism’s movements (). Additional interdisciplinary investigations by microbiologists and physicists have shown the contain a linear array of 15–20 membrane-bound vesicles along the cell’s long axis (see figure). Each vesicle, called a magnetosome, is an invagination © Jones & ofBartlett the cell membrane Learning, and containsLLC the protein machinery© to Jones nucleate &and Bartlett grow a magnetic Learning, crystal LLCof NOT FOR SALEmagnetite OR (Fe DISTRIBUTION3O4) or greigite (Fe3S4). The chain of magnetosomesNOT FOR is organized SALE by OR filaments DISTRIBUTION that are similar to eukaryotic . By running parallel to the magnetosome chain, the filaments organize the vesicles into a chain. As each vesicle accumulates the or greigite crystal to form a magneto- some, magnetostatic interactions between vesicles stabilizes the linear aggregation. As an aside, mag- netite is also found in migrating animals © Jones & Bartlett Learning,such as LLCbutterflies, homing pigeons, and© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONdolphins. NOT FOR SALE OR DISTRIBUTION To date, all magnetotactic bacterial cells are motile, gram-negative cells common in aquatic and marine , including where oxygen is absent.© Jones This last & observation Bartlett isLearning, particu- LLC © Jones & Bartlett Learning, LLC larlyNOT noteworthy FOR SALEbecause itOR explains DISTRIBUTION why NOT FOR SALE OR DISTRIBUTION these organisms have — they act as a compass needle to orient the cell. Recent studies have shown that mag- © Jones & Bartlettnetotactic bacteriaLearning, prefer LLClow concentra- © Jones & Bartlett Learning, LLC NOT FOR SALEtions of OR oxygen. DISTRIBUTION So, a current theory is NOT FOR SALE OR DISTRIBUTION that both magnetotaxis and aerotaxis work together to allow cells to “find” the optimal oxygen concentration, permiting the bacteria cells to reach a sort of bio- Bacterial magnetosomes (yellow) are seen in this false-color © Jones & Bartlett Learning,logical nirvanaLLC and settle in for a life of© Jonestransmission & Bartlett electron micrographLearning, of a magnetotacticLLC marine NOT FOR SALE OR DISTRIBUTIONenvironmental bliss. NOT spirillum.FOR SALE (Bar = 1 ORµm.) DISTRIBUTION

■ In conclusion, one of the take-home les- as making proteins? This requires two processes, sons ©from Jones the discussions & Bartlett of Learning, cell structur LLCe and that of © and Jones & Bartlett (Chapter Learning, 8). LLC functionNOT explored FOR SALE in this chapterOR DISTRIBUTION (and the initial In eukaryotic cells,NOT these FORprocesses SALE are spatiallyOR DISTRIBUTION discussion of the bacteria/eukaryote paradigm separated into the cell nucleus (transcription) and in Chapter 3) is the ability of bacterial and the cytoplasm (translation). archaeal organisms to carry out the “complex” In bacterial and archaeal cells, there also can © Jones &metabolic Bartlett and Learning, biochemical LLC processes typically be© spatial Jones separation & Bartlett between Learning, transcription LLC and NOT FORassociated SALE OR with DISTRIBUTION eukaryotic cells— usually with- translationNOT FOR FIGURE SALE 4.22 OR. The DISTRIBUTION RNA out the need for elaborate membrane-enclosed molecules needed for transcription are localized subcompartments. to a region separate from the ribosomes and other However, there is now clear evidence for an proteins that perform translation. In fact, stud- intricate and sophisticated subcellular architec- ies indicate that transcription is localized to the © Jones & Bartlett Learning,ture in the LLC domains Bacteria and Archaea.© Jones But & peripheryBartlett Learning,of the nucleoid. LLC So, even without a NOT FOR SALE OR DISTRIBUTIONwhat about other major cellular processesNOT suchFOR SALEnuclear OR membrane, DISTRIBUTION these cells can separate the

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.6 The Cell Cytoplasm and Internal Structures 123

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION4.5: Public Health NOT FOR SALE OR DISTRIBUTION The Wall-less Cytoskeleton

Sometimes the lack of something can speak loudly. Take for example the mycoplasmas such as that causes primary (walking pneumonia). This species, as well as other Mycoplasma species, lack© Jonesa cell wall. & How Bartlett then can Learning, they maintain LLC a defined cell shape (see figure)?© Jones & Bartlett Learning, LLC Transmission electronNOT microscopy FOR SALEhas revealed OR that DISTRIBUTION mycoplasmal cells contain a very complexNOT cyto- FOR SALE OR DISTRIBUTION skeleton and further investigations indicate the cytoskeletal proteins are very different from the typical cytoskeletal homologs found in other groups of the Firmicutes. For example, citri, which causes infections in other animals, has a fibril protein cytoskeleton that is laid down as a helical ribbon. This fibril protein has not been found in any other organisms. Because the cells are spiral shaped, the ribbon© Jonesprobably is& laid Bartlett down in Learning,such a LLC © Jones & Bartlett Learning, LLC way NOTto determine FOR cellSALE shape, OR suggesting DISTRIBUTION NOT FOR SALE OR DISTRIBUTION that shape does not have to be totally dependent on a cell wall. In , which © Jones &is Bartlett closely related Learning, to M. pneumoniae LLC © Jones & Bartlett Learning, LLC and causes human urethral infections, NOT FOR aSALE eukaryotic-like OR DISTRIBUTION tubulin homolog NOT FOR SALE OR DISTRIBUTION has been identified, but none of the other proteins have been identified that it recruits at the division neck for cell division. Surprising?© JonesNot really. & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Important? Immensely!NOT Because FOR myco- SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION plasmas do not have a cell wall, why would they require those proteins that lay down a peptidoglycan cross wall between cells? So the lack of something (wall-©forming Jones proteins) & Bartlett tells us Learning, what LLC © Jones & Bartlett Learning, LLC thoseNOT proteins FOR must SALE do in theirOR gram-DISTRIBUTIONFalse-color scanning electron micrographNOT of FOR Mycoplasma SALE pneu- OR DISTRIBUTION positive relatives that do have walls. moniae cells. (Bar = 2.5 µm.)

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

(A) FIGURE 4.21 A Bacterial Cytoskeleton. Bacterial cells have© protein Joness similar & Bartlettto those that Learning, form the eukaryotic LLC © Jones & Bartlett Learning, LLC cytoskeleton.NOT FOR (A) Microfilament-like SALE OR DISTRIBUTION proteins form helical NOT FOR SALE OR DISTRIBUTION filaments that curve around the edges of these cells of Bacillus subtilis. (Bar = 1.5 µm.) (B) Three-dimensional model of a helical cell (green) with a helical cytoskeletal filament of crescentin (pink). »» What would be the shape of these cells without the © Jones &cytoskeletal Bartlett proteins? Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT(B) FOR SALE OR DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 124 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT TABLEFOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4.3 A Summary of the Structural Features of Bacterial and Archaeal Cells Structure Chemical Composition Function Comment External Structures © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Pilus Protein Attachment to surfaces Found primarily in NOT FOR SALE OR DISTRIBUTION Genetic transfer gram-negativeNOT FOR bacteriaSALE OR DISTRIBUTION Flagellum Protein Motility Present in many rods and spirilla; few cocci; vary in number and placement Glycocalyx Polysaccharides and small proteins Buffer to environment Capsule and slime layer © Jones & Bartlett Learning, LLC Attachment to© surfaces Jones & Bartlett Contributes Learning, to disease LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE development OR DISTRIBUTION Found in plaque bacteria and biofilms Cell Envelope Cell wall Cell protection © Jones & Bartlett Learning, LLC © Jones Shape determination & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT Cell FOR lysis prevention SALE OR DISTRIBUTION Bacterial Gram positives: thick Site of activity of penicillin peptidoglycan and teichoic and lysozyme acid Gram negatives: little peptidoglycan Gram-negative bacteria and© Jones an outer & membrane Bartlett Learning, LLC release© Jones endotoxins & Bartlett Learning, LLC Archaeal PseudopeptidoglycanNOT FOR SALE OR DISTRIBUTION S-layerNOT FOR SALE OR DISTRIBUTION Protein Cell membrane Bacterial Protein and Cell boundary Lipid bilayer Archaeal phospholipid Transport into/out of cell Lipid bilayer/monolayer Site of enzymatic reactions Internal Structures© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Nucleoid NOT FOR SALE DNA OR DISTRIBUTION Site of essentialNOT genes FOR SALE Exists ORas single, DISTRIBUTION closed loop chromosome Plasmid DNA Site of nonessential genes R plasmids Ribosome RNA and protein Protein synthesis Inhibited by certain antibiotics © JonesMicrocompartment & Bartlett Learning, Various LLC metabolic enzymes © Jones & Bartlett Learning, Enzymes LLC are enclosed in a NOT FOR SALE OR DISTRIBUTION NOT Retention FOR ofSALE volatile OR or DISTRIBUTION protein shell toxic metabolites Inclusion Glycogen, sulfur, lipid Nutrient storage Used as nutrients during starvation periods Metachromatic granule Polyphosphate Storage of polyphosphate Found in diphtheria bacilli © Jones & Bartlett Learning, and LLC calcium ions © Jones & Bartlett Learning, LLC Gas ProteinNOT FORshell SALE OR DISTRIBUTION Buoyancy HelpsNOT cells FOR remain SALE buoyant OR DISTRIBUTION Magnetosome Magnetite/greigite Cell orientation Helps locate preferred Cytoskeleton Proteins Cell division, chromosomal Functionally similar to segregation, cell shape eukaryotic cytoskeletal © Jones & Bartlett Learning, LLC © Jones & Bartlett proteins Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 4.6 The Cell Cytoplasm and Internal Structures 125

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORprocess SALE involved OR DISTRIBUTION in making cellular proteins, in a NOT FOR SALE OR DISTRIBUTION manner similar to eukaryotic cells. Traditionally, a was an organism without a cell nucleus; that is, without a membrane surrounding the DNA or chromosome. But is that a fair way to describe all bacterial© Jones and archaeal& Bartlett organ- Learning, LLC © Jones & Bartlett Learning, LLC isms? In this chapter, youNOT have FOR learned SALE that thereOR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION are many basic differences between bacterial and archaeal cells, yet do we lump them together just because they both lack a cell nucleus? Some sci- entists ©say Jones no—the & terms Bartlett “prokaryote” Learning, and “pro-LLC © Jones & Bartlett Learning, LLC karyotic” are not appropriate for these two domains NOT FOR SALE OR DISTRIBUTIONFIGURE 4.22 Spatial SeparationNOT FOR of Transcription SALE OR and DISTRIBUTION of life. Translation. In these cells of Bacillus subtilis, fluores- So, to finish this chapter, take a look at cence microscopy was used to identify RNA polymerase (transcription) using a red fluorescent protein and ribo- MICROINQUIRY 4, which discusses the prokaryotic/ somes (translation) using a green fluorescent protein. eukaryotic model for living organisms. Separate subcompartments are evident. (Bar = 3 µm.) © Jones & Bartlett Learning, LLC »» What© Jonesdoes the spatial& Bartlett separation Learning, indicate concerning LLC NOT FOR SALE OR DISTRIBUTION compartmentation?NOT FOR SALE OR DISTRIBUTION

INQUIRY 4 The Prokaryote/Eukaryote© Jones Model & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION “It is now clear that among organisms Instead of two kinds of organisms— there are two different organizational pat- prokaryotes and eukaryotes—there are terns of cells, which Chatton . . . called, three: Bacteria, Archaea, and Eukarya. with singular prescience, the eukaryotic and In 2006, Norm Pace, a molecular biolo- prokaryotic© Jones type. The& Bartlett distinctive Learning,property LLC © Jones & gistBartlett turned evolutionistLearning, at LLC the University of bacteriaNOT andFOR blue-green SALE algae OR is DISTRIBUTION the NOT FOR SALEof Colorado, OR Boulder,DISTRIBUTION suggested that the prokaryotic nature of their cells. It is on massive data bank of gene sequences this basis that they can be clearly segre- identified since 1995 shows just how dif- gated from all other protists (namely, other ferent archaeal organisms are from bac- algae, and fungi), which have terial organisms and, in some ways, the © Jones &eukaryotic Bartlett cells.” Learning, LLC © Jones & Bartlett Learning,archaeal LLC ones are more similar to eukary- NOT FOR SALE OR DISTRIBUTIONStanier and van Niel (1962) NOT FOR SALE OR DISTRIBUTIONotic organisms. Therefore, Pace says, “we —The concept of a bacterium. need to reassess our understanding of the course of evolution at the most fun- The idea of a tree of life extends back damental level.” Among items needing centuries and originates not with scien- reassessment is the prokaryotic/eukaryotic tific thinking, but rather© withJones folklore & Bartlettand Learning, LLC paradigm—the© Jones tradition& Bartlett (folklore) Learning, if you LLC culture, and often focusedNOT on FORimmortality SALE OR DISTRIBUTION will—thatNOT FORif an organism SALE isOR not DISTRIBUTIONa eukary- or fertility (see figure). ote, it must be a prokaryote. The development of the three domains The quote at the top of the page in tree of life, on the other hand, rep- refers to Edouard Chatton who coined resents the evolutionary relationships Glass mosaic of tree of life on a wall of the the terms “prokaryotic” and “eukaryotic.” between© Jones species. & Its Bartlett development Learning, has LLC16th century Sim Wat Xiang Thong© Luang Jones & Interestingly,Bartlett Learning, neither he, norLLC Stanier and madeNOT a profound FOR change SALE in ORbiology. DISTRIBUTION Prabang UNESCO World Heritage Site,NOT Laos. FOR SALEvan Niel, OR ever DISTRIBUTION really made mention as to

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© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION 126 CHAPTER 4 Cell Structure and Function in the Bacteria and Archaea

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOTwhat FOR a prokaryotic SALE OR cell DISTRIBUTIONis. Yet if you look Archaea and, therefore,NOT should FOR not SALEbe put ORDiscussion DISTRIBUTION Point in any introductory biology textbook, under the umbrella of “prokaryote.” There is no doubt that bacterial and ar- prokaryote is defined as a group of organ- Pace believes that saying prokary- chaeal organisms are very different enti- isms that lack a cell nucleus. According otes lack a cell nucleus is a scientifically ties. So, if “prokaryote” is to be deleted to Pace, “the prokaryote/eukaryote model invalid description; although open to from the biological vocabulary, what can for biological diversity and evolution© Jones is & Bartlettdebate, he saysLearning, no one can LLC define what we call the© Bacteria Jones and & Archaea? Bartlett Can Learning, LLC invalid.” How can all organismsNOT without FOR SALEa prokaryote OR DISTRIBUTIONis—only what it is not you think ofNOT some FOR positive SALE characters OR that DISTRIBUTION a cell nucleus be called “prokaryotic,” (e.g., no nucleus, no mitochondria, no would define both bacterial and archaeal especially because the eukaryotic cell chloroplasts, no endomembrane system, cells? If so, then how about inventing a nucleus appears to be descended from as etc.). Therefore, lumping the Bacteria common noun and adjective for both? ancient a line of cells as the Archaea? Yes, and Archaea conceptually dismisses the Or do we simply speak of the bacteria, the concept ©of aJones nuclear membrane& Bartlett (or Learning,fundamental LLC and important differences© Jones archaea, & Bartlett and eukaryotes Learning, separately? LLC not) is important,NOT but FOR no more SALE important OR DISTRIBUTION between these two kinds of organisms NOTand FOR SALE OR DISTRIBUTION than other cellular properties. And the reinforces an incorrect understanding of problem is that the word “prokaryote” is biological organization and evolution. so engrained in the culture of biology and Pace believes it is to delete the in the scientific mind of —and term prokaryote as a term for bacterial and © Jonesstudents—that & Bartlett inappropriate Learning, inferences LLC archaeal organisms. ©Because Jones it has & longBartlett Learning, LLC NOTabout FOR organisms SALE areOR made DISTRIBUTION using this term. been used by all biologyNOT texts, FOR including SALE OR DISTRIBUTION Pace does not buy the argument that the this one (although in many cases “bacte- term “prokaryote” can be used to identify ria” and “archaea” have replaced the term organisms that are not eukaryotes because prokaryote), Pace says he realizes “it is the Bacteria are very different from the hard to stop using the word, prokaryote.” © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

SUMMARY© Jones OF & KEY Bartlett CONCEPTS Learning, LLC © Jones & Bartlett Learning, LLC 4.1 DiversityNOT Among FOR the SALE Bacteria OR and DISTRIBUTIONArchaea 6. One orNOT more flagella FOR, foundSALE on manyOR rodsDISTRIBUTION and spirals, 1. The phylogenetic tree of life contains many bacterial phyla provide for cell motility. Each flagellum consists of a and groups, including the Proteobacteria, Gram-positive basal body attached to the flagellar filament. In nature, bacteria, Cyanobacteria, Chlamydiae, and Spirochaetes. flagella propel bacterial cells toward nutrient sources 2. Many organisms in the domain Archaea live in extreme (chemotaxis). Spirochetes have endoflagella, while other © Jones &environments. Bartlett Learning, The Euryarchaeota LLC (methanogens, extreme © Jones bacterial& Bartlett species Learning, undergo gliding LLC motility. halophiles, hyperthermophiles, and the thermoacidophiles) 7. The glycocalyx is a sticky layer of polysaccharides NOT FOR SALEand the Crenarchaeota OR DISTRIBUTION are the two phyla. NOT FORthat SALE protects OR the cellDISTRIBUTION against desiccation, attaches it 4.2 Cell Shapes and Arrangements to surfaces, and helps evade immune cell attack. The glycocalyx can be thick and tightly bound to the cell 3. Bacilli have a cylindrical shape and can remain as (capsule) or thinner and loosely bound (slime layer). single cells or be arranged into diplobacilli or chains (streptobacilli). Cocci are spherical and form a variety of 4.5 The Cell Envelope arrangements, including© the Jones diplococcus & ,Bartlett streptococcus Learning,, LLC8. The cell wall provides structure© Jones and protects & againstBartlett cell lysis. Learning, LLC and staphylococcus. The spiral-shaped bacteria can be Gram-positive bacteria have a thick wall of peptidoglycan curved rods () orNOT spirals (FORspirochetes SALE and ORspirilla DISTRIBUTION). strengthened with teichoicNOT acids. Gram-negativeFOR SALE cells OR have DISTRIBUTION Spirals generally appear as single cells. a single layer of peptidoglycan and an outer membrane 4.3 An Overview to Bacterial and Archaeal Cell Structure containing lipopolysaccharide and porin proteins. 9. Archaeal cell walls lack peptidoglycan but may have either 4. Cell organization is centered on three specific processes: a or S-layer. sensing and responding to environmental changes, compartmentalizing© Jones & Bartlettmetabolism, Learning,and growing and LLC 10. The cell© membrane Jones represents& Bartlett a permeability Learning, barrier LLCand the reproducing. site of transfer for nutrients and metabolites into and out of NOT FOR SALE OR DISTRIBUTION the cell.NOT The cell FOR membrane SALE reflects OR the DISTRIBUTION fluid mosaic model 4.4 External Cell Structures for membrane structure in that the lipids are fluid and the 5. Pili are short hair-like appendages found on many gram- proteins are a mosaic that can move laterally in the bilayer. negative bacteria to facilitate attachment to a surface. 11. The archaeal cell membrane links lipids through an ether Conjugation pili are used for genetic transfer of DNA. linkage and the lipid tails may be bonded together into a © Jones & Bartlett Learning, LLC © Jones single& Bartlett monolayer Learning,. LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION Step A: Self-Test 127

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4.6 The Cell Cytoplasm and Internal Structures 14. Ribosomes carry out protein synthesis, microcompartments 12. The DNA (bacterial chromosome), located in the nucleoid, sequester species-specific processes, while inclusions store is the essential genetic information and represents most of nutrients or structural building blocks. the organism’s genome. 15. The cytoskeleton, containing protein homologs to 13. Bacterial and archaeal cells may contain one or more the cytoskeletal proteins in eukaryotic cells, helps plasmids, circular© Jonespieces of nonessential& Bartlett DNA Learning, that replicate LLC determine cell shape,© Jones regulates &cell Bartlett division, and Learning, controls LLC independently ofNOT the chromosome. FOR SALE OR DISTRIBUTION chromosomal segregationNOT FORduring cellSALE division. OR DISTRIBUTION

LEARNING© Jones & BartlettOBJECTIVES Learning, LLC © Jones & Bartlett Learning, LLC After understandingNOT FOR the SALE textbook OR reading, DISTRIBUTION you should be capable of 8. CompareNOT and FOR contrast SALE the structure OR DISTRIBUTION of a gram-positive cell wall writing a paragraph that includes the appropriate terms and pertinent with a gram-negative cell wall. information to answer the objective. 9. Summarize the differences between bacterial and archaeal cell walls. 1. Identify the major bacterial phyla described in this chapter and 10. Justify the need for a cell membrane surrounding all bacterial provide characteristics for each group. and archaeal cells. © Jones &2. Bartlett Explain why Learning, many archaeal LLC organisms are considered extremo-© Jones11. & Explain Bartlett how theLearning, structure of archaealLLC cell membranes differs from NOT FOR SALEphiles .OR DISTRIBUTION NOT FOR SALEbacterial cellOR membranes. DISTRIBUTION 3. Compare the various shapes and arrangements of bacterial and 12. Describe the structure of the nucleoid. archaeal cells. 13. Judge the usefulness of plasmids to cell metabolism and organ- 4. Summarize how the processes of sensing and responding to the ismal survival. environment, compartmentation of metabolism, and growth and 14. List the typical microcompartments and inclusions found in metabolism are linked© to Jones cell structure. & Bartlett Learning, LLC the bacterial cell cytoplasm© Jones and identify & Bartletttheir contents Learning, or roles. LLC 5. Assess the role of pili to bacterial colonization and infection. 15. Describe three roles that the bacterial cytoskeleton plays. 6. Describe the structureNOT of bacterial FOR flagella SALE and OR discuss DISTRIBUTION how they NOT FOR SALE OR DISTRIBUTION function in chemotaxis. 7. Differentiate between a capsule and slime layer. Identify their roles in cell survival.

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION For STEPS A–D, answers to even-numbered questions and problems can be found in Appendix C on the Student Companion Website at http://microbiology.jbpub.com/bodysystems2e/. In addition, the site features eLearning, an online review area that provides quizzes and other tools to help you study for your class. You can also follow useful links for in-depth information, © Jonesread & Bartlett more MicroFocus Learning, stories, LLC or just find out the latest ©microbiology Jones & Bartlettnews. Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

STEP A: SELF-TEST Each of the following questions is designed to assess your ability to 3. Spherical bacterial cells in chains would be referred to as a _____ remember or recall factual© or Jonesconceptual & knowledge Bartlett related Learning, to this LLC arrangement. © Jones & Bartlett Learning, LLC chapter. Read each question carefully, then select the one answer A. vibrio that best fits the questionNOT or statement. FOR SALE OR DISTRIBUTION B. streptococcus NOT FOR SALE OR DISTRIBUTION 1. Which one of the following is NOT a genus within the gram-positive C. staphylococcus bacteria? D. tetrad A. Staphylococcus 4. Intracellular organization in bacterial and archaeal species is centered B. Methanogens around ______. C.© MycoplasmaJones & Bartlett Learning, LLC A. © compartmentation Jones & Bartlett of metabolism Learning, LLC D. Bacillus and Clostridium B. growth and reproduction 2. TheNOT domain FOR Archaea SALE includes OR all DISTRIBUTION the following groups except the C. NOT sensing FORand responding SALE toOR environment DISTRIBUTION ______. D. All the above (A–C) are correct. A. mycoplasmas B. extreme halophiles C. Crenarchaeota © Jones & BartlettD. Euryarchaeota Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 5. Which one of the following statements does NOT apply to pili? 11. When comparing bacterial and archaeal cell membranes, only A. Pili are made of protein. archaeal cell membranes ______. B. Pili allow for attachment to surfaces. A. have three layers of phospholipids C. Pili facilitate nutrient transport. B. have a phospholipid bilayer D. Pili contain adhesins. C. are fluid 6. Flagella are ______. © Jones & Bartlett Learning, LLCD. have ether linkages © Jones & Bartlett Learning, LLC A. made of carbohydrate andNOT lipid FOR SALE OR DISTRIBUTION12. Which one of the following statementsNOT FORabout the SALE nucleoid OR is NOT DISTRIBUTION B. found on all bacterial cells true? C. shorter than pili A. It contains a DNA chromosome. D. important for chemotaxis B. It represents a nonmembranous subcompartment. 7. Capsules are similar to pili because both ______. C. It represents an area devoid of ribosomes. A. contain DNA D. It contains nonessential genetic information. B. are made© Jonesof protein & Bartlett Learning, LLC 13. Plasmids ______.© Jones & Bartlett Learning, LLC C. containNOT dextran FOR fibers SALE OR DISTRIBUTION A. replicateNOT with the FOR bacterial SALE chromosome OR DISTRIBUTION D. permit attachment to surfaces B. contain essential growth information 8. Gram-negative bacterial cells would stain _____ with the C. may contain antibiotic resistance genes and have _____ in the wall. D. are as large as the bacterial chromosome A. orange-red; teichoic acid 14. Which one of the following is NOT a structure or subcompartment B. orange-red; lipopolysaccharide found in bacterial cells? © Jones C. &; Bartlett peptidoglycan Learning, LLC © JonesA. Microcompartments & Bartlett Learning, LLC NOT FORD. purple; SALE teichoic OR acidDISTRIBUTION NOT FORB. Volutin SALE OR DISTRIBUTION 9. The cell membrane of archaeal hyperthermophiles contains ______. C. Ribosomes A. a monolayer D. Mitochondria B. 15. The bacterial cytoskeleton ______. C. ester linkages A. transports vesicles D. All the above (A–C) are correct. B. helps determine cell shape 10. The movement of glucose into© a cellJones occurs & by Bartlett______. Learning, LLCC. is organized identical to its ©eukaryotic Jones counterpart & Bartlett Learning, LLC A. NOT FOR SALE OR DISTRIBUTION D. centers the nucleoid NOT FOR SALE OR DISTRIBUTION B. active transport C. simple diffusion D. phospholipid exchange

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION STEP B: REVIEW 16. Construct a concept map for the domain Bacteria using the fol- 17. Construct a concept map for the Cell Envelope using the follow- lowing terms. ing terms. © JonesActinobacteria & Bartlett Learning,hyperthermophiles LLC © Jonesactive & transport Bartlett Learning, membrane LLC proteins Bacillus Mycoplasma cell membrane NAG NOT FORblooms SALE OR DISTRIBUTIONProteobacteria NOT FORcell wall SALE OR DISTRIBUTION NAM Chlamydiae rickettsiae endotoxin outer membrane Cyanobacteria Spirochaetes facilitated transport peptidoglycan Escherichia Staphylococcus fluid-mosaic model periplasm Firmicutes Streptomyces gram-negative wall phospholipids gram-negative species ©Treponema Jones & Bartlett Learning, LLCgram-positive wall polysaccharide© Jones & Bartlett Learning, LLC gram-positive species lipid A porin proteins NOT FOR SALE OR DISTRIBUTIONlipopolysaccharide (LPS) teichoicNOT FORacid SALE OR DISTRIBUTION

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© Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION Step D: Questions for Thought and Discussion 129

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Identify and label the structure on the accompanying bacterial cell from each of the following descriptions. Some separate descriptions may apply to the same structure. Descriptions 18. Is involved with nutrient© Jones storage. & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 19. An essential structureNOT for chemotaxis, FOR SALE aerotaxis, OR or phototaxis.DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 20. Contains nonessential genetic information that provides genetic variability. 21. The structure that synthesizes proteins. 22. The protein structures used for attachment to surfaces. 23. Contains© Jones essential & Bartlettgenes for metabolism Learning, and growth. LLC © Jones & Bartlett Learning, LLC 24. Prevents cell desiccation. 25. ANOT 70S . FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 26. Contains peptidoglycan. 27. Regulates the passage of substances into and out of the cell. 28. Extrachromosomal loops of DNA. 29. Represents a capsule or slime layer. © Jones &30. Bartlett The semifluid Learning, mass of proteins, LLC amino acids, sugars, salts, and© ions Jones & Bartlett Learning, LLC NOT FOR SALEdissolved OR in water.DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION STEP C: APPLICATIONS 31. A bacterial species has been isolated from a patient and identi- 33. In the research lab, the gene for the cytoskeletal protein similar fied as a gram-positive rod. Knowing that it is a , to eukaryotic tubulin is transferred into the DNA chromosome of a what© Jones structures & would Bartlett it most Learning, likely have? Explain LLC your reasons coccus-shaped© Jones bacterium. & Bartlett When Learning,this cell undergoes LLC cell division, forNOT each FORchoice. SALE OR DISTRIBUTION predictNOT what FOR shape SALE the daughter OR cellsDISTRIBUTION will exhibit. Explain your 32. Another patient has a blood infection caused by a gram-negative answer. bacterial species. Why might it be dangerous to prescribe an anti- biotic to treat the infection?

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION STEP D: QUESTIONS FOR THOUGHT AND DISCUSSION 34. In reading a story about a bacterial species that causes a human 36. Why has it taken so long for microbiologists to discover micro- disease, the word “bacillus” is used. How would you know if the compartments and a cytoskeleton in bacterial and archaeal cells? article is referring to ©a bacterial Jones shape & Bartlett or a bacterial Learning, genus? LLC37. Apply the current understanding© Jones of the &bacteria/eukaryote Bartlett Learning, paradigm LLC 35. Suppose this chapter onNOT the structure FOR SALEof bacterial OR and DISTRIBUTIONarchaeal cells to the following statement:NOT “Studying FOR SALE the diversity OR ofDISTRIBUTION life only had been written in 1940, before the electron microscope became accentuates life’s unity.” available. Which parts of the chapter would probably be missing?

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