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

Topics in This Chapter © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Some Basic Biological The Microbe isNOT so very FOR small SALE OR DISTRIBUTION NOT PrinciplesFOR SALE OR DISTRIBUTION You cannot make him out at all, Cell Theory But many sanguine people hope Metabolic Diversity Requirement for Oxygen To© Jonessee him & down Bartlett a microscope. Learning, LLC © Jones & BartlettGenetic Learning, Information LLC Oh!NOT Let FOR us never,SALE neverOR DISTRIBUTION doubt NOT FOR SALE ORWhat DISTRIBUTION Makes a Microbe? What nobody is sure about! Procaryotic and Eucary- —Hilaire Belloc, More Beasts for Worse Children otic Cells Microbial Evolution and © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLCDiversity NOT FOR SALEPreview OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Introducing the Microbes In the introductory section the term microbe has been used extensively because Prions this text is about microbes, particularly those relatively few that are pathogens. Viruses The term microbe was not deﬁ ned or even adequately described, but the six groups Bacteria of microbes were ©named—prions, Jones & Bartlett viruses, Learning, bacteria, protozoans, LLC unicellular algae, © JonesProtozoans & Bartlett Learning, LLC and fungi. (Worms,NOT biologically FOR SALE known OR as helminths,DISTRIBUTION are frequently included in NOTAlgae FOR SALE OR DISTRIBUTION microbiology texts even though they are not microbes because a number of Fungi species cause infections resembling microbial infections.)

Photo courtesy of Janice Haney Carr/CDC.

73338_CH02.indd 29 20/11/12 4:19 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONSome Basic BiologicalNOT PrinciplesFOR SALE OR DISTRIBUTION Cell Theory To further understand microbes, whether pathogens or not, it is necessary to review © Jonesa few& Bartlettvery basic Learning, concepts of biology,LLC because all microbes© are Jones biological & Bartlett packages Learning, LLC NOT FORwith SALE certain ORunique DISTRIBUTION characteristics. Cells are considered theNOT basic FOR unit of SALE life, based OR DISTRIBUTION on the observations of Robert Hooke in 1665. Hooke used the word cella in his examination of cork, which revealed tiny compartments that reminded him of the cells in which monks lived. His studies ultimately gave rise to the cell theory, a fundamen- © Jones & Bartlett Learning,tal concept in LLC biology, as postulated by Matthias© Jones Schleiden & Bartlett and Theodor Learning, Schwann LLC NOT FOR SALE OR(1838) DISTRIBUTION and Rudolf Virchow (1858). The majorNOT points FOR of SALEthe cell theoryOR DISTRIBUTION are as follows: 1. All organisms are composed of fundamental units called cells. 2. All organisms are unicellular (single cells) or multicellular (more than one cell). © Jones & Bartlett Learning, LLC 3. All cells are fundamentally© Jones alike& Bartlett with regard Learning, to their structure LLC and their NOT FOR SALE OR DISTRIBUTION metabolism. NOT FOR SALE OR DISTRIBUTION 4. Cells arise only from previously existing cells (“life begets life”). “Life begets life” is a refutation of the doctrine of spontaneous generation, a concept that was disproved by the end of the nineteenth century. An understand- © Jonesing & of Bartlett the cell theory Learning, is the basis LLC for an understanding of ©life, Jones including & Bartlettmicrobial Learning, LLC NOT FORlife. SALEThe cell OR theory DISTRIBUTION does not apply to viruses and prions;NOT they FOR are described SALE OR as DISTRIBUTION acellular, subcellular, or as biological agents, terms that are used somewhat inter- changeably. Nevertheless, as a matter of convenience license is sometimes taken, and they are described as microbes or microorganisms. Viruses are not considered by scientists as being “alive,” but they come close; they are in that gray area be- © Jones & Bartlett Learning,tween living LLCand nonliving. Prions are even© Jonesless biologically & Bartlett complex Learning, than viruses. LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Metabolic Diversity The term life is elusive and cannot be given an exact defi nition; at best, it can only be described. Nevertheless, several attributes are associated with living systems that, © Jones & Bartlett Learning, LLCcollectively, establish life.© By Jones one strategy & Bartlett or another Learning, all organisms LLC exhibit these NOT FOR SALE OR DISTRIBUTIONcharacteristics, summarizedNOT in TABLEFOR 2.1 SALE. A major OR property DISTRIBUTION of life is the ability to constantly satisfy the requirement for energy. It takes energy for every cell to stay alive, whether it is a single cell or a component of a multicellular organism; in the latter case each cell contributes to the total energy requirement of the organism. Your © Jonesbody & constantlyBartlett Learning,expends energy. LLC © Jones & Bartlett Learning, LLC NOT FOR ItSALE takes energy OR DISTRIBUTION to breathe even during sleep and for the NOTheart toFOR constantly SALE push OR DISTRIBUTION blood through an interconnected and tortuous maze of blood vessels. Because you don’t fi ll up at the gas station, it’s obvious that your energy is derived from the foods you eat. Through a complex series of biochemical reactions, the body metabolizes the organic compounds (proteins, fats, and carbohydrates) of your diet and releases the AUTHOR’S NOTE© Jones (RIK) & Bartlett Learning,energy stored LLC in their chemical bonds into© a Jonesbiologically & Bartlettavailable high-energy Learning, com- LLC Even when you doze in class, it takes energy to keep from slitheringNOT out FOR of your chair SALE and onto OR poundDISTRIBUTION known as adenosine triphosphate (NOTATP); FORyou live SALE directly OR off ofDISTRIBUTION this and con- the fl oor. I have seen this happen only once in stantly replace it as you take in nutrients. Most organisms, including most microbes, all my years at the lecture podium. are heterotrophs, meaning that they require organic compounds as an energy source;

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NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Inorganic TABLE 2.1 Characteristics of Life Solar chemical energy energy Characteristic Description Cellular organization The cell is the basic unit of life; organisms are © Jones & Bartlettunicellular Learning, or multicellular. LLC © Jones & Bartlett Learning, LLC Energy productionNOT FOR SALEOrganisms OR DISTRIBUTION require energy and a biochemical NOT FOR SALE OR DISTRIBUTION strategy to meet their energy requirement. Photosynthetic Chemosynthetic autotrophs autotrophs Reproduction Organisms have the capacity to reproduce by asexual or sexual methods and in doing so pass on genetic material (DNA) to Autotrophs © Jones & Bartlett Learning,their LLC progeny. © Jones & Bartlett Learning, LLC Irritability Organisms respond to internal and external Organic NOT FOR SALE OR DISTRIBUTIONstimuli. NOT FOR SALE OR DISTRIBUTION (C6H12O6 + O2) Growth and development Organisms grow and develop in each new generation; specialization and differentiation Heterotrophs occur in multicellular organisms. Inorganic © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC (CO2 + H2O) NOT FOR SALEhumans OR are DISTRIBUTION heterotrophs. Other microorganisms andNOT plant FOR life are SALE autotrophs OR andDISTRIBUTION do not require organic compounds, but they do require energy. Some are able to FIGURE 2.1 A pathway map showing directly use the energy of the sun (photosynthetic autotrophs), and others derive heterotroph dependency on autotrophs energy from the metabolism of inorganic compounds (chemosynthetic auto- and the autotrophs’ energy sources. trophs). In so doing autotrophs produce organic compounds and oxygen (O2). Hence, heterotrophs© Jonesare dependent & Bartlett on autotrophs Learning, for energy LLC (FIGURE 2.1). © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Requirement for Oxygen

In addition to metabolic diversity, organisms exhibit diversity in their O2 requirement. The “higher” organisms that are more familiar to you are aerobes, meaning © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC they require O2 for their metabolic activities. Some bacteria are anaerobes and do notNOT require FOR oxygen; SALE other OR anaerob DISTRIBUTIONes are actually killed by O2. FacultativeNOT anaerobes FOR SALE OR DISTRIBUTION are bacteria that grow better in the presence of O2 but can shift their metabolism, allowing them to grow in the absence of O2. Knowledge of the oxygen requirements of pathogens is important in clinical microbiology. For © Jones & Bartlettexample, Learning,specimens LLCfrom infections caused by© bacteriaJones & Bartlett Learning, LLC suspected of being anaerobes must be transported and cultured NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION under anaerobic conditions (FIGURE 2.2).

Genetic Information

The genetic information© Jones for &the Bartlett structure Learning, and functioning LLC © Jones & Bartlett Learning, LLC of all cells is storedNOT in molecules FOR SALE of deoxyribonucleic OR DISTRIBUTION acid NOT FOR SALE OR DISTRIBUTION (DNA), a large and complex organic molecule. Genes are segments of the DNA molecule. Since the establishment of DNA as the hereditary material, the expression “life begets life” can be expanded to explain the mechanism by which a particular life form FIGURE 2.2 Culturing anaerobic gives© Jones rise to &the Bartlett same life Learning,form; that is, LLC tomatoes produce tomatoes,© humans Jones pro- & Bartlettbacteria. Learning, Some bacteria LLCcannot grow in the presence of oxygen. The GasPak duceNOT humans, FOR SALE and Escherichia OR DISTRIBUTION coli produces Escherichia coli. Each ofNOT these FOR groups SALE tray OR is a meansDISTRIBUTION of culturing anaerobes. has its characteristics embedded in DNA that confer its identity. The DNA is Courtesy and © Becton, Dickinson, transferred, by a variety of reproductive strategies, from parent to offspring. and Company.

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73338_CH02.indd 31 20/11/12 4:19 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONWhat Makes a Microbe?NOT FOR SALE OR DISTRIBUTION

With these basic biological principles in mind, the term microbe (or microorganism) can now be better described. The question to be considered is what makes a microbe © Jonesa microbe? & Bartlett As will Learning, become apparent, LLC this question is not easily© Jones answered. & Bartlett Your fi rst Learning, LLC NOT FORresponse SALE may OR be DISTRIBUTION“they are all too small to be seen withoutNOT a microscope” FOR SALE or areOR DISTRIBUTION microscopic . Wrong. At fi rst thought this would appear to be true, but what about the algae and the fungi? Are fungi microscopic? No doubt you have seen molds (FIGURE 2.3) classifi ed as fungi, growing on food left too long in the refrigerator or per- © Jones & Bartlett Learning, LLC haps on a pair of old© Jonessneakers & that Bartlett you forgot Learning, about in theLLC NOT FOR SALE OR DISTRIBUTION dank basement or NOThidden FOR away SALEin a dormitory OR DISTRIBUTION closet. They are macroscopic; that is, they can be seen with the naked eye. Hence, “microscopic” is not a distinguishing microbial characteristic. To describe all microbes as being unicellular is also © Jones & Bartlett Learning, LLC not© correct Jones because & Bartlett the fungi Learning, and many of LLC the algal forms are macroscopic and clearly multicellular. (As pointed out later, NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION some fungi, namely yeasts, are unicellular.) These organisms must be multicellular; if they were unicellular, that one cell would be enormous—a ridiculous idea! There are exceptions to the rule that all bacteria are © Jones & Bartlett Learning,unicellular LLC and microscopic. This might© Jones seem like& Bartlett an amaz- Learning, LLC NOT FOR SALE OR DISTRIBUTIONing fi sh story, but in 1985 a large cigar-shapedNOT FOR microorgan- SALE OR DISTRIBUTION FIGURE 2.3 Mold growing on a tomato. © Jones & Bartlett Learning. ism was found in the guts of the Red Sea brown surgeonfi sh. This organism was subsequently identifi ed as a bacterium, approximately a million times larger in volume than E. coli, and was christened Epulopiscium fi shelsoni. Twelve years later, © Jones & Bartlett Learning,in 1997, an evenLLC more monstrous bacterium© Jones was discovered & Bartlett in sediment Learning, samples LLC residing off the coast of Namibia (BOX 2.1); the organism has the tongue-twisting NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION name Thiomargarita namibiensis and to date is one for the Guinness Book of World Records. They are visible to the naked eye. To give you some idea of size relationships, if an ordinary bacterium were the size of a baby mouse, E. fi shelsoni would be equivalent to a lion and T. namibiensis would © Jones & Bartlett Learning, LLCbe the size of a blue whale,© the Jones world’s & largest Bartlett animal. Learning, The blue whale LLC measures up to NOT FOR SALE OR DISTRIBUTION90 feet (29 meters) and weighsNOT aboutFOR 120 SALE tons. ORHow DISTRIBUTIONmany cells might make up such an enormous creature? The number would be in the trillions. Each of these cells exhibits the same fundamental life characteristics as the single microbe. Microbes are sometimes described as “simple” because many consist of only a single cell or are less than a cell (viruses and prions). Consider, however, that this single cell must fulfi ll all © Jonesthe & functions Bartlett of life.Learning, On the other LLC hand, in a multicellular organism© Jones (like & the Bartlett whale), Learning, LLC NOT FORalthough SALE each OR cell DISTRIBUTIONfulfi lls all the criteria for life, there is a “sharing”NOT of FOR function SALE because OR DISTRIBUTION of specialization into a variety of cell types (for example, muscle cells, nerve cells, and blood cells). Perhaps that makes life easier. Hence, single-celled organisms, and even those multicellular organisms consisting of only a small number of cells without © Jones & Bartlett Learning, evidence of trueLLC specialization, are simple ©only Jones in the &sense Bartlett of numbers Learning, and not inLLC a NOT FOR SALE OR physiologicalDISTRIBUTION (functional) sense. NOT FOR SALE OR DISTRIBUTION So, if microbes are not necessarily microscopic and/or unicellular, then what is a microbe? There really is no unifying principle or precise defi nition. The term

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73338_CH02.indd 32 20/11/12 4:19 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION BOX 2.1 “Monster” Bacteria

If asked to describe bacteria, just about everyone would Both epulos and the sulfur pearl are anomalies in the reply that they are too small to be seen without a micro- bacterial world. The sizes of cells of all kinds, not only bacte- scope. However, in© 1985 Jones Epulopiscium & Bartlett fi shelsoni, Learning, a giant LLCrial cells, are limited by the© surface Jones area & of Bartlett the membrane, Learning, LLC bacterium that canNOT be seen FOR without SALE a microscope, OR DISTRIBUTION was because nutrients and wasteNOT are FORtransported SALE in and OR out DISTRIBUTION of discovered in the guts of surgeonfi sh in the warm waters the cells by diffusion across the cell membrane. As cells in- of the Red Sea and off the coast of Australia. The organ- crease in size, both volume and surface area increase, but ism can grow to about 500 micrometers, or about the surface area increases to a lesser degree than does volume. size© Jones of the period & Bartlett at the end Learning, of this sentence. LLC To give you At some ©point Jones the surface & Bartlett area becomes Learning, too limited LLC to allow someNOT idea FOR of size,SALE one OR scientist DISTRIBUTION projected that “if ordi- for suffi cientNOT diffusion FOR between SALE theOR cell DISTRIBUTION and its environment. nary bacteria were mouse sized, E. fi shelsoni would be So how did E. fi shelsoni and T. namibiensis manage to equivalent to a lion.” This organism is referred to as become so big? What are the physiological adaptations? In “epulos” and was originally thought to be protozoan-like. the case of epulos, microscopic examination reveals that However, analysis of their DNA revealed that they are, in the cell membrane, rather than being stretched smoothly © Jones & Bartlettfact, bacteria. Learning, LLC © Jonesaround & Bartlett the cell, isLearning, convoluted (wrinkled), LLC resulting in “hills NOT FOR SALEIn OR 1997 DISTRIBUTION Thiomargarita namibiensis stole the prizeNOT for FORand valleys,”SALE aOR phenomenon DISTRIBUTION that greatly increases cell sur- size from Epulopiscium. This “monster” bacterium, ap- face. (This adaptation is not unique to bacterial cells; the proximately the size of a fruit fl y’s head, was discovered in surface of the human brain is highly convoluted, resulting samples of sediment in the greenish ooze off the coast in a greater surface area, a factor that correlates with spe- of Namibia in Africa.© Jones These spherical& Bartlett cells Learning, range from LLCcies intelligence.) The large© size Jones of T. namibiensis & Bartlett is attrib-Learning, LLC 100 to 750 micrometersNOT FOR in size. SALE Dispersed OR DISTRIBUTIONthroughout uted to the presence of aNOT large flFOR uid-fi lled SALE sac occupying OR DISTRIBUTION their cytoplasm are globules of sulfur. The bacteria tend to over 90% of the cell’s interior. The sac is packed with ni- organize into strands of cells that glisten white from light trate that the cell uses in its metabolism to produce energy, refl ected off their sulfur globules, which explains the name. making it less dependent on constant diffusion across the T. namibiensis means Namibian sulfur pearl. membrane to transport nutrients and waste. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION microbe, or microorganism, is a term of convenience used to describe biological agents, in a collective sense, that in general are too small to be seen without the aid of a microscope. The term is also used for microbes that are cultured and identifi ed using similar techniques. Based on what has been presented here, it is clear © Jones & Bartlettthat these Learning, descriptions LLC are not always true. Some biologists© Jones consider & Bartlett microbes Learning, to LLC NOT FOR SALEbe organisms OR DISTRIBUTION that are at less than the tissue level ofNOT organization. FOR SALE This statementOR DISTRIBUTION requires some explanation and is based on what is referred to as “biological hierarchy,” or levels of biological organization. Recall that a cell is the fundamental unit of biological organization and that groups of cells establish© Jones multicellularity. & Bartlett Consider Learning, the human, LLC or any other multi- ©AUTHOR’S Jones NOTE & (RIK) Bartlett Learning, LLC cellular animal or plant, and it is obvious that in addition to an increase in cell Some years ago I attended the annual meeting NOT FOR SALE OR DISTRIBUTION NOTof the American FOR Society SALE for Microbiology OR DISTRIBUTION in numbers, the process of differentiation and specialization has taken place. For ex- Miami Beach, Florida and overheard two airport ample, over 200 cell types make up the human, including red blood cells, fi ve cate- baggage handlers commenting that about gories of white blood cells, epithelial cells, connective tissue cells, nerve cells, and twelve thousand microbiologists were expected to attend. One asked the other, “What’s a muscle cells. All these cells, as stated in the cell theory, share common fundamental microbiologist, anyway?” to which the other characteristics,© Jones & Bartlettbut superimposed Learning, on their LLC basic structure and function© Jones is a special- & Bartlettreplied, “Beats Learning, me! I suppose it’sLLC a small biologist.” Several miles from the airport was a izationNOT FORof structure SALE and OR function. DISTRIBUTION Cells of the same type constitute NOTthe tissue FOR level SALE huge ORbillboard DISTRIBUTION with the words “Orkin Pest of organization, as exemplifi ed by nerve tissue, blood tissue, and connective tissue. Control welcomes microbiologists.” It was a Tissues in turn constitute organs, structures composed of more than one tissue memorable meeting.

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NOT FORFIGURE SALE2.4 Levels OR of biological DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Multicellular Unicellular organisms organization. (a) Microbes. Subcellular organisms (b) Multicellular. Protozoa Algae © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Prions NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Viruses (a) Bacteria

Cells Tissues Organs Systems

Smooth muscle Smooth muscle © Jones & Bartlett Learning,Adipose LLC (fat) cell © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Lungs Connective

Macrophage Kidneys Digestive © Jones & Bartlett Learning, LLC(b) © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION MULTICELLULAR

type; the heart, brain, stomach, and kidney are examples. Organs in turn constitute © Jonesorgan & Bartlett systems, aLearning, collection of LLCorgans that contribute to an overall© Jones function & Bartlett or func- Learning, LLC tions. The digestive system, nervous system, respiratory system, excretory system, NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION and reproductive system are examples familiar to you. This hierarchy is summarized as follows and is further illustrated in FIGURE 2.4: subcellular ➝ cells ➝ tissues ➝ organs ➝ organ systems. All microbes are devoid of tissues. That is, they are all at the subcellular or © Jones & Bartlett Learning,cellular level LLC of organization, although fungi© Jones and some & Bartlettalgae hint Learning,at specialization LLC NOT FOR SALE OR andDISTRIBUTION approach the tissue level of organizatNOTion. PrionsFOR SALEand viruses OR can DISTRIBUTION be properly placed at the acellular or subcellular level, which, simply put, means that they are less than cells and are at the threshold of life.

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73338_CH02.indd 34 20/11/12 4:19 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEProcaryotic OR DISTRIBUTION and Eucaryotic Cells NOT FOR SALE OR DISTRIBUTION

Biologists recognize the existence of two very distinct types of cells, referred to as procaryotic and eucaryotic cells (Greek, pro, before, + karyon, nut or kernel, + eu, true). Procaryotic© Jones cells have& Bartlett a simpler Learning, morphology LLC than eucaryotic cells and © Jones & Bartlett Learning, LLC are primarily distinguishedNOT FOR by SALE the fact OR that DISTRIBUTION there is no membrane around the NOT FOR SALE OR DISTRIBUTION nucleus. There is a nuclear area rich in DNA that serves as the carrier of genetic information, as in all cells, but that DNA is not enclosed within a nuclear membrane. This DNA-rich area is referred to as a nucleoid rather than as a true nucleus. Further, in procaryotic cells there are no membrane-bound cellular structures© Jones (organelles) & Bartlett in Learning,contrast to the LLC cellular anatomy of the eucaryotic© Jones cells. & Bartlett Learning, LLC NOTProcaryotic FOR SALE and eucaryoticOR DISTRIBUTION cells are compared in TABLE 2.2 andNOT in FIGURE FOR 2.5 SALE. OR DISTRIBUTION Bacteria are procaryotic microorganisms; protozoans, unicellular algae, fungi, and all other forms of life (except viruses and prions) are composed of eucaryotic cells.

© Jones & BartlettMicrobial Learning, Evolution LLC and Diversity © Jones & Bartlett Learning, LLC NOT FOR SALEProcaryotes OR DISTRIBUTION date back 3.5 billion years and were theNOT only FORlife forms SALE for 2.5OR billion DISTRIBUTION years; they are the ancestors of eucaryotes. Aristotle pondered the relationships among organisms, as do scientists today. In the eighteenth century the botanist Carolus Linnaeus classifi ed all life forms as belonging to either the plant or the animal kingdom.© (Students Jones would& Bartlett be delighted Learning, if only LLCthis were the case today!) © Jones & Bartlett Learning, LLC Microbes were largelyNOT ignored FOR SALEbecause ORlittle DISTRIBUTION was known about them, but, because NOT FOR SALE OR DISTRIBUTION they had to be placed somewhere, they were considered plants, probably because those that had been observed possessed cell walls. Various schemes of classifi cation have been proposed over the last few centuries, and taxonomy, the science of classifi cation, became more and more complex. In 1866 Ernst Haeckel proposed a three-kingdom© Jones & Bartlett system—animals, Learning, plants, LLC and a new kingdom, Protista,© Jones a collection & Bartlett Learning, LLC toNOT accommodate FOR SALE microbes. OR DISTRIBUTIONIn the light of modern biology, it becameNOT apparent FOR that SALE OR DISTRIBUTION

TABLE 2.2 Comparison of Procaryotic and Eucaryotic Cells

© Jones & BartlettCharacteristic Learning, Procaryotes LLC ©Eucaryotes Jones & Bartlett Learning, LLC NOT FOR SALELife formOR DISTRIBUTIONBacteria, Archaea NOTAll microbial FOR cellsSALE (with OR the DISTRIBUTION exception of bacteria, viruses, and prions) and all other cells Nucleus DNA chromosome but not Chromosome present and © Jonesenveloped & Bartlettby membrane Learning,enveloped LLC by membrane © Jones & Bartlett Learning, LLC Cell sizeNOT About FOR 1–10 SALE micrometers OR DISTRIBUTION Over 100 micrometers NOT FOR SALE OR DISTRIBUTION Chromosomes Single circular DNA (two Multiple paired chromosomes chromosomes in a few) present in nucleus Cell division Asexual binary ﬁ ssion; no Cell division by mitosis; sexual “true” sexual reproduction reproduction by meiosis ©Internal Jones compart- & BartlettNo membrane- Learning, bound LLC internal Organelles bound© by Jones & Bartlett Learning, LLC NOTmentalization FOR SALE ORcompartments DISTRIBUTION membrane NOT FOR SALE OR DISTRIBUTION Ribosomes Smaller than eucaryotic cells Membrane bound and free and not membrane bound

© Jones & Bartlett Learning, LLC ©CHAPTER Jones &2 Bartlett The Microbial Learning, World LLC 35 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

73338_CH02.indd 35 20/11/12 4:19 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Centrioles Microtubules Flagellum Golgi apparatus

Nuclear pore Basal body © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC

FIGURE 2.5 Schematic drawingsNOT of (a) a FOReucaryotic SALE OR DISTRIBUTION NOT FreeFOR ribosomes SALE OR DISTRIBUTION Mitochondrion cell and (b) a procaryotic cell. Lysosome Nuclear envelope DNA (chromosomes) Ribosome Nucleolus © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Cytoplasm NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTIONRibosomes attached to endoplasmic reticulum

Plasma © Jones & Bartlett Learning, LLC membrane© Jones & Bartlett Learning, LLC Cell membrane NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTIONCilia Cell wall Actin filaments

Rough endoplasmic Smooth endoplasmic (a) DNA (chromosome) (b) reticulum reticulum

© Jones & Bartlett Learning, LLC even three kingdoms were© Jones not enough. & Bartlett In 1969 Learning, LLC NOT FOR SALE OR DISTRIBUTIONa fi ve-kingdom systemNOT was proposed FOR SALE by Robert OR DISTRIBUTION ANIMALIAFUNGI PLANTAE Whittaker and initially accepted by most biologists. This classifi cation describes organisms as belonging to the kingdoms Monera, Protista, Vertebrates FIGURE 2.6 © JonesInsects & BartlettMushrooms Learning, LLC Fungi,© Animalia,Jones & and Bartlett Plantae (Learning,). Recall LLC that microbes consist of six groups accom- NOT FOR SALE OR DISTRIBUTIONMosses NOT FOR SALE OR DISTRIBUTION Flowering modated in one of Whittaker’s fi ve kingdoms plants Molluscs as follows: Bacteria are classifi ed as Monera, Green algae protozoans and unicellular algae are classifi ed as Protista, and fungi are classifi ed as © Jones & BartlettFlatworms Learning, LLCYeasts © Jones &Fungi. Bartlett Note Learning,that viruses LLCand prions are not NOT FORRoundworms SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Molds considered in this scheme of classifi cation, because they are neither procaryotic nor eu- Eucaryotic, caryotic cells but are subcellular. Red "multicellular" The 1950s ushered in the tide of molec- algae organisms © Jones & Bartlett Learning, LLC ular biology, and its© wake Jones introduced & Bartlett new Learning, LLC PROTISTA NOT FOR SALE OR DISTRIBUTIONEucaryotic, techniques. BiologistNOT Carl Woese FOR andSALE his col- OR DISTRIBUTION Unicellular algae unicellular leagues at the University of Illinois focused Protozoa organisms in on ribosomal ribonucleic acid (rRNA) as MONERA Prokaryotic a “fi ngerprint” to identify shared character- Cyanobacteria Bacteria organisms istics of microbes and thus gain insight into © Jones & Bartlett Learning, LLC their© relatedness, Jones & whichBartlett in turn Learning, would point LLC NOT FORUNIVERSAL SALE ANCESTOROR DISTRIBUTION to theirNOT evolutionary FOR SALE history. OR DISTRIBUTION In 1990 Woese, along with Otto Kandler FIGURE 2.6 Whittaker’s fi ve- kingdom system. and Mark L. Wheelis, proposed a novel

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73338_CH02.indd 36 20/11/12 4:19 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEscheme OR of DISTRIBUTIONclassifi cation based Bacteria (Eubacteria)NOT FOR Archaea SALE (Archaebacteria) OR DISTRIBUTION Eucarya on Woese’ analysis. The Woese system assigns all organisms to one of three domains or “su- perkingdoms”—the© Jones Bacteria &, Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Archaea (formerlyNOT Archaebac- FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION teria), and Eucarya (FIGURE 2.7), all of which arose from a single ancestral line. (All of Whittaker’s fi ve traditional kingdoms can be© reassignedJones & among Bartlett the Learning,three LLC © Jones & Bartlett Learning, LLC domains.)NOT FOR The SALE Bacteria OR and DISTRIBUTION the NOT FOR SALE OR DISTRIBUTION Eucarya fi rst diverged from an ancestral stock, followed by the divergence of the Archaea from © Jones & Bartlettthe Eucarya Learning, line. The LLCdomains © JonesUniversal & ancestor Bartlett Learning, LLC NOT FOR SALEdiffer ORremarkably DISTRIBUTION from one another in their chemicalNOT composition FOR SALE and OR in otherDISTRIBUTION FIGURE 2.7 Woese’s three- domain system. characteristics, as summarized in TABLE 2.3. The term bacteria as commonly used includes both the bacteria and the archaea. It should be apparent that classifi cation, particularly at the level of microorganisms, is not cast in concrete but is constantly under revision as new information becomes available. It© is Jonesa credit to & the Bartlett scientifi cLearning, process that reevaluationLLC is the name of © Jones & Bartlett Learning, LLC the game. Admittedly,NOT it isFOR confusing, SALE but OR to quoteDISTRIBUTION William Shakespeare (who prob- NOT FOR SALE OR DISTRIBUTION ably never even took a course in biology), “What’s in a name? That which we call a rose by any other name would smell as sweet.” So you need not sweat it too much! No matter what the classifi cation, bacteria were the fi rst forms of life on Earth. Fossilized bacteria© Jones have & been Bartlett discovered Learning, in stromatolites LLC , stratifi ed rocks dating ©back Jones 3.5 billion & Bartlett Learning, LLC toNOT 3.8 billion FOR years, SALE a long OR time DISTRIBUTION ago in the history of the estimated 4.6 billion-year-oldNOT FOR SALE OR DISTRIBUTION planet Earth. When life arose, the Earth’s ancient atmosphere contained little or no free oxygen but consisted principally of carbon dioxide and nitrogen with smaller

TABLE 2.3 Comparisons of Bacteria, Archaea, and Eucaryaa © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONMembrane- AntibioticNOT FOR SALE OR DISTRIBUTION Domain bound Nucleus Cell Wall Susceptibility Characteristic Bacteria No Present Yes Large number of bacterial species Archaea No Present No “Extreme” bacteria © Jones & Bartlett Learning, LLC growing in high- © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONsalt environment NOT FOR SALE OR DISTRIBUTION and at extreme temperatures Eucarya No Variable No (some Algae (most), fungi, exceptions in protozoans, © Jones & Bartlett Learning, LLC fungi) “higher”© Jones animals & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION and NOTplants FOR SALE OR DISTRIBUTION aMajor differences are present in the biochemistry of cell walls, cell membranes, genetic material, and structures in the cytoplasm.

© Jones & Bartlett Learning, LLC ©CHAPTER Jones &2 Bartlett The Microbial Learning, World LLC 37 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

73338_CH02.indd 37 20/11/12 4:19 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION amounts of gases, including hydrogen (H2), hydrogen sulfi de (H2S), and carbon monoxide (CO). This ancient atmosphere, devoid of O2, would not have sup- ported life as we know it. Only microbes that were able to meet their energy requirements with non-oxygen-requiring chemical reactions populated the © Jones primordial & Bartlett environment. Learning, The LLC early microbes were photosynthetic© Jones and & used Bartlett water Learning, LLC NOT FORand SALEcarbon ORdioxide DISTRIBUTION (CO2) in photosynthetic reactions, resultingNOT FOR in the SALE produc- OR DISTRIBUTION tion of O2 and carbohydrates. This process was responsible for the generation of O2 in the Earth’s atmosphere approximately two billion years ago. FIGURE 2.8 (a) Pyrocoecus furiosus, Since their origin on Earth billions of years ago, bacteria have exhibited re- a highly heat-resistant bacterium. markable diversity and have fi lled every known ecological niche. Yet, according to © Eye of Science/Photo© Jones Researchers, & Bartlett Learning,some estimates, LLC fewer than 2% of microbes© Jones have been & Bartlettidentifi ed Learning,and even fewer LLC Inc. (b) PsychrophilicNOT FOR Methanococ- SALE ORhave DISTRIBUTION been cultured and studied. PerhapsNOT you FORcan recall SALE the ORold MotherDISTRIBUTION Goose coides burtonii discovered in 1992 in Ace Lake, Antartica, can survive in nursing rhyme “Peas Porridge Hot” which states “some like it hot and some like it temperatures as low as –2.5˚C. cold.” (Ask your instructor to sing it while you fall asleep in class!) It’s like the di- © Dr. M. Rohde, GBF/Photo versity in bacteria. Bacteria belonging to the domain Archaea continue to be found © JonesResearchers, & Bartlett Inc. Learning, LLCin environments once considered© Jones too & extremeBartlett or Learning, too harsh for LLC life at any level. In NOT FOR SALE OR DISTRIBUTION mostNOT cases FOR these SALE organisms, OR DISTRIBUTION extremophiles, cannot be grown by existing culture techniques; evidence of their presence has been obtained by molecular biology techniques that allow scientists to examine minute amounts of their deposited ribonucleic acid (RNA). Some like it hot © Jones & Bartlett Learning,and are LLC called hyperthermophiles© (“heatJones lovers”). & Bartlett Some Learning, LLC NOT FOR SALE OR DISTRIBUTIONhyperthermophiles have been identifiNOT ed inFOR the hotSALE springs OR DISTRIBUTION in Yellowstone Park where the temperatures exceed 70°C. Some microbes do best at temperatures even higher, above 100°C. Thermus aquaticus was isolated from hot springs © Jones & Bartlett Learning, LLC in the 1960s. It produced© Jones an & enzyme Bartlett (Taq Learning, polymerase LLC), NOT FOR SALE OR DISTRIBUTION which is essentialNOT to a FORvery important SALE OR technique DISTRIBUTION (polymerase chain reaction; PCR) in molecular biology allowing for rapid DNA synthesis and sequencing. Pyrococcus furiosus lives in boiling water bubbling from undersea hot (a) vents and freezes to death in temperatures below 70°C © Jones & Bartlett Learning, LLC (FIGURE © Jones 2.8a). Some& Bartlett extremophiles, Learning, the psychrophiles LLC , like it NOT FOR SALE OR DISTRIBUTION cold.NOT Psychrophiles FOR SALE have OR growth DISTRIBUTION temperatures lower than –20°C and are happy in Arctic and Antarctic environments (Figure 2.8b). Finally, if you like tongue-twisters, try your tongue around Psychromonas ingrahamii and Colwellia © Jones & Bartlett Learning,psychrerythraea, LLC both at home and© livingJones comfortably & Bartlett in Learning, LLC NOT FOR SALE OR DISTRIBUTIONfrigid waters. Some bacteria are extremeNOT FORhalophiles SALE (“salt OR DISTRIBUTION lovers”) (FIGURE 2.9), and some produce methane gas in their metabolism. These bizarre examples indicate that many of the archaea live at the extremes of life zones (BOX 2.2). Archaea have not been implicated as disease pro- © Jones & Bartlett Learning, LLC ducers and are not© further Jones considered & Bartlett in this Learning, text. LLC NOT FOR SALE OR DISTRIBUTION In 2010, NASANOT scientists FOR SALEreported OR the DISTRIBUTION discovery of bacteria that could substitute arsenic for phosphorous, a (b) necessary component of DNA. If correct, the fi nding

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73338_CH02.indd 38 20/11/12 4:19 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FORFIGURE 2.9SALE The Dead OR Sea. DISTRIBUTION This sea has a salt concentration well above that found in the Great Salt Lake in Utah; it lies farther below sea level than any other terrestrial spot on Earth. You can lie on your back and ﬂ oat without any effort. Amazingly, this extreme environment is home for a variety of halophilic bacteria. Author’s photo (RIK). © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

BOX 2.2 Some Bizarre Bacteria © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALESome ORmicrobes DISTRIBUTION exhibit an unusual lifestyle and remarkableNOT characteristics FOR SALE that OR provide DISTRIBUTION fascinating stories and illustrate the tremendous diversity of the microbial world. Consider Deinococcus radiodurans, a bacterium further described in Box 2.3, that can survive a dose of radiation greater than 3,000 times the dose that can kill a human. The Dead Sea, characterized by its extreme salinity, is erroneously named; it is not dead at all but teems with salt-loving (halophilic) bacteria. You will be surprised to learn that microbes can © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC grow in your car’s battery acid or that some bacteria thrive on arsenic. How about magnetotactic bacteria? They manufac- ture minute, iron-containingNOT FOR magnetic SALE particles OR DISTRIBUTIONused as compasses by which the organismsNOT align FORthemselves SALE to the OR Earth’s DISTRIBUTION geomagnetic fi eld. These curious microbes prefer life in the deeper parts of their aquatic environment where there is less oxygen. Their magnetic compass points the way. And then there are the as yet unnamed bacteria living in symbiotic partnership with giant tube worms, as long as 2 meters, living© Jones in the hydrothermal & Bartlett vents Learning, of the ocean LLC fl oor. As these worms mature,© Jonestheir entire & digestiveBartlett tract Learning, disappears, LLCincluding theirNOT mouth FOR and SALE anal openings. OR DISTRIBUTION Now that presents a problem, and it’s bacteriaNOT FORto the rescue!SALE The OR tissues DISTRIBUTION of the worm are loaded with bacteria that obtain energy from the surrounding chemical environment suffi cient for their own needs and for those of their worm hosts. In turn, the worms provide a safe harbor for the bacteria, ensure an adequate environment for energy production, and provide nitrogen-rich waste materials, allowing for synthesis of microbial cellular components—a great mutualistic arrangement. © Jones & BartlettHere Learning,is a strange storyLLC about Serratia marcescens,© Jones a bacterium & Bartlett whose Learning, LLC NOT FOR SALEcolonies OR form DISTRIBUTION a deep red pigment when grown in moistNOT environments. FOR SALE In 1263 OR DISTRIBUTION in the Italian town of Bolsena a priest was celebrating Mass. When he broke the communion wafers he found what he thought was blood on them and assumed it to be the blood of Christ. Given the lack of scientifi c knowledge during the Dark Ages,© Jones it is understandable & Bartlett Learning, the event was LLC regarded as a © Jones & Bartlett Learning, LLC miracle. It was not NOTa miracle FOR at all. SALE The red-pigment-producing OR DISTRIBUTION S. marcescens NOT FOR SALE OR DISTRIBUTION had contaminated the wafers during their storage in the dampness of the ancient church (FIGURE B2.2). Nevertheless, Raphael’s painting The Miracle of Bolsena, depicting this event, hangs on a wall in the Vatican. Here’s another story of an unusual bacterium, Shewanella, reported in June 2011. These microbes© Jones use & metal Bartlett ions inLearning, place of oxygen LLC in their metabolism and© in Jones so & Bartlett Learning, LLC doing,NOT FORcan minimize SALE ORsome DISTRIBUTION toxic metals from migrating into soilNOT and FORFIGURE SALEB2.2 A culture OR ofDISTRIBUTION Serratia marcescens. groundwaters—a nice example of bacteria used for clean-up. Courtesy of Jeffrey Pommerville.

© Jones & Bartlett Learning, LLC ©CHAPTER Jones &2 Bartlett The Microbial Learning, World LLC 39 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

73338_CH02.indd 39 20/11/12 4:19 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION BOX 2.3 Conan the Bacterium

Conan the Barbarian, a 1982 movie starring Arnold agency has a pretty big toxic cleanup problem at its waste Schwarzenegger, was the ﬁ rst Conan movie. In this fantasy development sites.” Genes from bacteria that can digest story, from the mythical ©age Jones of sword & andBartlett sorcery, Learning, Arnie toxic LLC waste but cannot survive radiation© Jones have & been Bartlett geneti- Learning, LLC portrays Conan as only ArnieNOT can FOR do! SALE OR DISTRIBUTIONcally engineered into D. radiodurans,NOT resulting FOR SALE in bacteria OR DISTRIBUTION Deinococcus radiodurans has been nicknamed “Conan that can transform toxic mercury into a nontoxic form and the bacterium”; it is one of nature’s “toughest cookies.” It unstable uranium into a stable form. These genetically can survive the rigors of being completely dried out, have its engineered bacteria are powerful tools in cleaning up the chromosomes© Jones disrupted, & Bartlett and be exposed Learning, to 1.5 million LLC rads three thousand© wasteJones sites & containingBartlett millionsLearning, of cubic LLC of radiation,NOT a FOR dose 3,000SALE times OR greater DISTRIBUTION than that which yards of contaminatedNOT FOR soil andSALE contaminated OR DISTRIBUTION groundwa- would kill a human. Further, it can transform toxic mercury ter estimated to be in the trillions of gallons. The ability of into a less toxic form, a feature especially useful at nuclear D. radiodurans to repair its own DNA is of interest to biolo- waste sites. According to Owen White of the Institute for Ge- gists because the process provides an insight into the nomic Research in Rockville, Maryland, “The Department of mechanisms of aging and into the biology of cancer. © JonesEnergy & Bartlett is very jazzedLearning, about D. LLC radiodurans, because the © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

would open up a new form of life on earth. Other scientists were skeptical about the study, so the role of arsenic-loving bacteria remains open. Here is another © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC strange story. Deinococcus radiodurans is a bacterium that can withstand 3,000 NOT FORtimes SALE more gammaOR DISTRIBUTION radiation than that which would killNOT a human FOR because SALE of ORits DISTRIBUTION unique ability to repair its damaged DNA. The scientists who study D. radiodurans have dubbed it “Conan the bacterium” (BOX 2.3). You may not like to hear this, but the human mouth is considered one of the © Jones & Bartlett Learning,most diverse LLC ecosystems and rivals the biological© Jones diversity & Bartlett of tropical Learning, rainforests. LLC NOT FOR SALE OR WithinDISTRIBUTION the past few years, scientists atNOT Stanford FOR UniversitySALE OR have DISTRIBUTION discovered 37 new organisms in the mouth, pushing the total to more than 500. These new microbes were found in the scum (plaque) in the deep gum pockets between teeth. (Your dentist would love this tidbit!) Their presence remained unknown simply because traditional culture methods do not allow their growth. Enterpris- © Jones & Bartlett Learning, LLCing microbiologists (sometimes© Jones known & Bartlett as plaq ueLearning, pickers) extracted LLC DNA from NOT FOR SALE OR DISTRIBUTIONplaque and mapped outNOT DNA FOR sequences, SALE revealing OR DISTRIBUTION bacteria that had not been previously known to inhabit the mouth. In fact, some new bacterial species were identifi ed, supporting the statement that less than 2% of the microbial popula- tion has been identifi ed. © Jones &A Bartlett comprehensive Learning, global microbialLLC survey to identify ©microbes Jones that & Bartlett make up Learning, LLC NOT FORthe biosphereSALE OR is underway DISTRIBUTION thanks to the cooperative effortNOT of the FOR National SALE Science OR DISTRIBUTION Foundation and the American Society for Microbiology. These two organizations are establishing a network of biodiversity research sites or “microbial observato- ries.” Other international efforts are in the works to develop a worldwide microbial inventory of genetic sequences. © Jones & Bartlett Learning,The origin LLC of life on Earth continues© toJones be a fascinating & Bartlett and Learning, mind-boggling LLC NOT FOR SALE OR questionDISTRIBUTION to which the explanation is purelNOTy speculative. FOR SALE The OR general DISTRIBUTION consensus among scientists is that the “primordial soup” hypothesis is the most likely explanation. In this hypothesis, organic compounds formed from a specifi c combination

© Jones &40 Bartlett Learning, LLCPART 1 The Challenge © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

73338_CH02.indd 40 20/11/12 4:20 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEof atmospheric OR DISTRIBUTION gases collected in water and sparkedNOT by FOR an energy SALE source. OR HowDISTRIBUTION exactly this happened is still debated. Another intriguing possibility is the hypothesis that Earth was seeded by life forms from Mars, the Red Planet. Photographs taken from the orbiting Mars Global Surveyor spacecraft© Jones indicated & Bartlett the possibility Learning, of water LLC just below the surface © Jones & Bartlett Learning, LLC of the planet. If, inNOT fact, FORMars has SALE water, OR it is DISTRIBUTION possible that the planet entertains, or NOT FOR SALE OR DISTRIBUTION entertained, life. According to the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder, “Mars meets all the requirements for life.” The possibility that life originated on Mars and was subsequently carried to Earth is plausible. Meteors and meteorites are constantly bombarding the Earth and some,© Jones originating & Bartlett from Mars’ Learning, surface, could LLC have transported ancestral© Jonesprocaryotic & Bartlett Learning, LLC cells.NOT Bacteria FOR SALEhave been OR cultured DISTRIBUTION out of Siberian and Antarctic permafrostsNOT FOR that SALE OR DISTRIBUTION have been in the deep freeze for millions of years. The National Aeronautic and Space Administration is now planning the Mars Sample Return Mission, which will bring Martian rocks back to Earth, and this will help to resolve the question of © Jones & Bartlettthe beginnings Learning, of life. LLC A famous and historic press© Jonesconference & Bartlettwas held Learning,at the LLC NOT FOR SALENational OR Aeronautic DISTRIBUTION and Space Administration in NOTWashington, FOR SALED.C. on ORAugust DISTRIBUTION 7, 1996, announcing that scientists had found evidence of ancient microbial life in a Mars meteorite known as ALH84001. Bear in mind, however, that the evidence was viewed by some authorities as weak and remains highly refuted. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Introducing theNOT Microbes FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION FIGURE 2.10 The microbial umbrella. Although there is no clear defi nition of microbes, it is time to introduce those biological agents that fall under the microbial umbrella© Jones (FIGURE & Bartlett 2.10 and TABLE Learning, 2.4). Algae LLCare © Jones & Bartlett Learning, LLC notNOT discussed FOR SALEin detail OR in this DISTRIBUTION text beyond NOT FOR SALE OR DISTRIBUTION this section, although they are highly signifi cant in terms of food chains and other benefi cial aspects. Further, some fungi are Subcellular Eucaryotic human pathogens, and many contribute © Jones & Bartlettto the death Learning, toll of patientsLLC with AIDS. © Jones & BartlettPrions Learning, LLC NOT FOR SALEWith ORthe exception DISTRIBUTION of viruses and prions, NOT FOR SALE OR DISTRIBUTION all microbes have both DNA and RNA, as do all cells. Microbes are measured in very small Viruses Algae units of the metric© system Jones called & Bartlett microm- Learning,Procaryotic LLC © Jones & Bartlett Learning, LLC eters (equal to oneNOT millionth FOR ofSALE a meter), OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION abbreviated as µm, and nanometers (equal to 1 billionth of a meter), abbreviated as nm. A meter is equivalent to about 39 inches, so a micrometer is equal to one Bacteria millionth© Jones of & 39 Bartlett inches. These Learning, numbers LLC are © Jones & BartlettFungi Learning, LLC probablyNOT FOR not SALEvery meaningful OR DISTRIBUTION to you, be- NOT FOR SALE OR DISTRIBUTION

cause they do not allow you to appreciate Protozoa the size of microbes relative to more familiar

© Jones & Bartlett Learning, LLC ©CHAPTER Jones &2 Bartlett The Microbial Learning, World LLC 41 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

73338_CH02.indd 41 20/11/12 4:20 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORTABLE SALE 2.4 OR Comparison DISTRIBUTION of Microbial Groupsa NOT FOR SALE OR DISTRIBUTION

Characteristic Archaea Bacteria Protozoans Fungi Unicellular Algae Cell type Procaryotic Procaryotic Eucaryotic Eucaryotic Eucaryotic Size Microscopic© Jones & MicroscopicBartlett Learning,b Microscopic LLC Macroscopic© Jones Microscopic & Bartlett Learning, LLC Cell wall PresentNOT FOR SALE Present OR DISTRIBUTION Absent PresentNOT Present FOR SALE OR DISTRIBUTION Reproduction Mostly asexual Mostly asexual Sexual and Sexual and Asexual (binary ﬁ ssion) (binary ﬁ ssion) asexual asexual Energy process Variable Mostly heterotrophic Heterotrophic Heterotrophic Autotrophic a Viruses and prions are not cells and, therefore, are not included. b There are© a few Jones exceptions. & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

objects, but there are some points that may help you think in this scale. A spoon- ful of fertile soil contains trillions of microbes, and the number of microbes that © Jones & Bartlett Learning, LLCcan be accommodated on© theJones period & at Bartlett the end of Learning, this sentence LLC is in the millions. NOT FOR SALE OR DISTRIBUTIONFIGURE 2.11 indicates the relativeNOT sizeFOR of microbes.SALE OR The DISTRIBUTION monstrous bacteria described FIGURE 2.11 Comparison of sizes of earlier are exceptions. Bacteria are many times smaller than eucaryotic cells but different kinds of microorganisms (not are about ﬁ fty times (or more) larger than viruses. drawn to scale).

DNA double helix Protozoa Red blood Mold cells

NOT FOR SALE ORRod-shaped DISTRIBUTION and NOT FOR SALE OR DISTRIBUTION spherical-shaped bacteria Tapeworm

NOT FORCarbon SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION atom HIV

Fluke © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Glucose Rickettsia Cyanobacterium molecule NOT FOR SALE OR DISTRIBUTIONYeast NOT FOR SALE OR DISTRIBUTION Unicellular algae Colonial algae Atoms Viruses Bacterial and Multicellular Molecules archaeal organisms Protozoa Fungi organisms

0.1nm 1nm© Jones 10nm & Bartlett 100nm Learning,1μm 10 μLLCm 100μm 1mm 1cm© Jones 0.1m & Bartlett 1m 10mLearning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Electron microscope Unaided eye Light microscope

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73338_CH02.indd 42 20/11/12 4:20 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALESmallness OR DISTRIBUTION has its advantages. Smallness providesNOT a large FOR surface SALE area OR per DISTRIBUTION unit volume, allowing for rapid uptake of nutrients from the environment. E. coli, for example, has a surface-to-volume ratio about twenty times greater than that of human cells. And now for the introduction—from least to the most complicated. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Prions NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Prions are the most recent addition to the microbial list; some texts continue to FIGURE 2.12 A transmission place them with viruses for lack of a better place. But the awarding of the 1997 electron micrograph of smallpox Nobel Prize to Stanley Prusiner, who discovered these agents, legitimized them as (Variola) viruses. Courtesy of Dr. Fred Murphy/CDC. separate© Jones entities. & Bartlett The word Learning, prion is an abbreviationLLC for pro- © Jones & Bartlett Learning, LLC teinaceousNOT FOR infectious SALE ORparticles. DISTRIBUTION Prions are protein mole- NOT FOR SALE OR DISTRIBUTION cules and are devoid of both DNA and RNA; their lack of nucleic acid is their major (and most puzzling) biological property. Prions exist normally, primarily in the brain, as © Jones & Bartlettharmless Learning,proteins. Abnormal LLC prions convert normal© Jones pro- & Bartlett Learning, LLC teins into infectious, disease-producing proteins responsi- NOT FOR SALEble for OR mad DISTRIBUTION cow disease and dementia type diseasesNOT FORin SALE OR DISTRIBUTION humans and in other animals. Questions remain unan- swered regarding their biology.

Viruses © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION As frequently noted, viruses are not organisms; Figure 2.4 indicates their subcellular position. Two major distinguishing characteristics of viruses are that, in contrast to cells, they contain either RNA or DNA (never both) and, further, they© Jones are submicroscopic & Bartlett particlesLearning, and canLLC be seen only with © Jones & Bartlett Learning, LLC FIGURE 2.13 Lactobacillus bacteria. anNOT electron FOR microscope SALE OR ( FIGUREDISTRIBUTION 2.12). Some have an addi- NOT FOR SALE OR DISTRIBUTION © John Walsh/Photo Researchers, Inc. tional coat or envelope encompassing them. Viruses are described as obligate intracellular parasites, meaning they must be (obligate) inside living cells (intracellular) to repli- cate; they are not capable of autonomous replication. They © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC take over the metabolic machinery and reap the beneﬁ ts of NOT FOR SALEenergy OR production, DISTRIBUTION without any expenditure of energy,NOT FORby SALE OR DISTRIBUTION the host cell. Perhaps this is the ultimate in parasitism.

Bacteria © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Bacteria are the bestNOT known FOR of SALE the microbial. OR DISTRIBUTION They are mi- NOT FOR SALE OR DISTRIBUTION croscopic, unicellular, procaryotic, and have cell walls (with the exception of a single subgroup, the Mycoplasma). They reproduce asexually by binary ﬁ ssion. In terms of size, they can be seen with a regular (light) microscope (FIGURE 2.13). Many© Jones bacteria & Bartlett are heterotrophs Learning, and LLC use organic com- © Jones & Bartlett Learning, LLC poundsNOT FOR as a sourceSALE of OR energy. DISTRIBUTION Others are autotrophs and NOT FOR SALE OR DISTRIBUTION use the energy of the sun, whereas some derive energy from the use of inorganic substances. Although a number of

© Jones & Bartlett Learning, LLC ©CHAPTER Jones &2 Bartlett The Microbial Learning, World LLC 43 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

73338_CH02.indd 43 20/11/12 4:20 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOTbacteria FOR are SALEpathogens OR and DISTRIBUTION are the major subject of this text, the vast majority of bacteria are nonpathogenic and play essential roles in the environment without which life would not be possible. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONProtozoans NOT FOR SALE OR DISTRIBUTION Protozoans are unicellular and eucaryotic and are classi- ﬁ ed according to their means of locomotion (FIGURE 2.14). Their energy generation requires the utilization of or- © Jones & Bartlett Learning, LLC ganic compounds.© Jones Many &diseases, Bartlett including Learning, malaria, LLC NOT FOR SALE OR DISTRIBUTION sleeping sickness,NOT and FOR amebic SALE dysentery, OR DISTRIBUTIONare caused by protozoans.

Algae © Jones & Bartlett Learning, LLC ©Algae Jones are &photosynthetic Bartlett Learning, eucaryotes LLC and in the photo- NOT FOR SALE OR DISTRIBUTION NOTsynthetic FOR process SALE produce OR DISTRIBUTION oxygen and carbohydrates FIGURE 2.14 A colorized scanning used by forms requiring organic compounds. Hence, electron micrograph of a fl agellated they are highly signifi cant in the balance of nature. Dinofl agellates and diatoms Giardia protozoan adhering to an are examples of unicellular algae and fall under the umbrella of microbes intestinal epithelial cell. Courtesy of (FIGURE 2.15). Dinofl agellates (plankton) are the primary source of food in the Dr. Stan Erlandsen/CDC. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FORoceans SALE of the OR world. DISTRIBUTION Some algae are pathogenic for humansNOT indirectly. FOR For SALE example, OR DISTRIBUTION the toxin produced by the dinofl agellates that causes red tide, Gymnodinium breve, causes neurological disturbances and death in humans as a result of our consumption of fi sh and shellfi sh that had fed on the dinofl agellates. Another species of dinofl agellate, Pfi esteria piscicida, also referred to as the “cell from hell,” © Jones & Bartlett Learning,threatened the LLC fi shing industry in the eastern© Jones United & StatesBartlett in 1997. Learning, A bloom LLC of NOT FOR SALE OR theseDISTRIBUTION algae resulted in the release of largeNOT amounts FOR of SALEneurotoxin, OR causingDISTRIBUTION neurological symptoms in fi shermen and fear among consumers. FIGURE 2.15 Freshwater diatoms. Courtesy of Robert W. Pillsbury. Fungi © Jones & Bartlett Learning, LLC ©Fungi Jones are &eucaryotes. Bartlett Morphologically, Learning, LLC they can be di- NOT FOR SALE OR DISTRIBUTION NOTvided FOR into twoSALE groups, OR theDISTRIBUTION yeasts and the molds. The yeasts are unicellular and are larger than bacteria; many reproduce by budding. Molds are the most typical fungi and are multicellular, consisting of long, branched, and © Jones & Bartlett Learning,intertwined LLC fi laments called hyphae© Jones. In early & Bartlett schemes Learning, LLC NOT FOR SALE OR DISTRIBUTIONof classifi cation fungi were consideredNOT FOR plants, SALE primarily OR DISTRIBUTION because they have cell walls. However, their cell wall composition is quite different from that of plants and from the cell walls of bacteria. Fungi are highly signifi - cant in terms of food chains and have certain benefi cial © Jones & Bartlett Learning, LLC aspects. Some are© Jonespathogenic & Bartlettand cause Learning,diseases that LLCare NOT FOR SALE OR DISTRIBUTION diffi cult to treat;NOT others FOR play SALE a highly OR signifi DISTRIBUTION cant role as opportunistic pathogens (organisms that are not usu- ally considered to be pathogens), because, as in AIDS,

© Jones &44 Bartlett Learning, LLCPART 1 The Challenge © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

73338_CH02.indd 44 20/11/12 4:20 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEwhen ORthe immuneDISTRIBUTION system is depressed they causeNOT disease. FOR SALE OR DISTRIBUTION Molds played a major role in the aftermath of Hurricanes Katrina and Rita, rendering houses uninhabitable. Patches of mold threaten the prehistoric paintings of animals in the Lascaux Cave in Dordogne© Jones region & Bartlett of southwest Learning, France LLCand © Jones & Bartlett Learning, LLC museum curatorsNOT constantly FOR needSALE to ORguard DISTRIBUTION against mold NOT FOR SALE OR DISTRIBUTION intrusions. Mushrooms are a well-known group of fungi. Their diversity is unusual as demonstrated by a wide range of size, colors, and patterns on their cap (FIGURE 2.16). Many species are© edible.Jones The & termsBartlett bugs Learning,and germs are LLC part of our popular © Jones & Bartlett Learning, LLC speechNOT FORbut have SALE no scientifi OR DISTRIBUTION c meaning. It should be clear NOT FOR SALE OR DISTRIBUTION from the above descriptions that each group of microbes is distinct from the others. When your physician diagnoses you as having a “bug,” you might ask what kind. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning,FIGURE LLC 2.16 Two mushrooms NOT FOR SALEOverview OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTIONgrowing on a tree stump in a fi eld. Author’s photo (TS). The microbial world is remarkable for its extreme diversity, as is evident in the distinct characteristics of the six microbial groups—prions, viruses, bacteria, protozoans, unicellular algae, and fungi. Further, within each group there is consider- able diversity. Not© Jonesall microbes & Bartlett are unicellular Learning, and LLC microscopic; some are © Jones & Bartlett Learning, LLC multicellular andNOT macroscopic FOR SALE and others OR ar DISTRIBUTIONe subcellular and microscopic. In re- NOT FOR SALE OR DISTRIBUTION cent times “monster” bacteria have been found that are unique in being unicellular and macroscopic, a rare combination. Viruses and prions are subcellular and are not considered life forms. There is no clear defi nition of what makes a microbe a© microbe, Jones but & Bartlettit is clear thatLearning, they are allLLC at less than the tissue level© ofJones biological & Bartlett Learning, LLC organization.NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION All bacteria are procaryotic, and all other microbes are eucaryotic. (Viruses and prions are not cells and are neither procaryotic nor eucaryotic.) Taxonomy evolved from a two-kingdom system (in which bacteria were considered plants) to a fi ve-kingdom system, with various other schemes along the way; the trend has © Jones & Bartlettbeen toward Learning, recognizing LLC the uniqueness of microbes.© JonesWoese proposes & Bartlett a classifi Learning, ca- LLC NOT FOR SALEtion system OR DISTRIBUTION based on rRNA analysis and assigns bacteriaNOT FORto one SALE of three OR domains DISTRIBUTION and refl ects their evolutionary history. Since their origin on Earth microbes have adapted to extreme ecological diversity and can be isolated from all environments. Some live at the extremes— from hot springs ©to permafrost.Jones & Bartlett All organisms Learning, must meet LLC a basic requirement for © Jones & Bartlett Learning, LLC energy, and microbialNOT FORevolution SALE has ORfostered DISTRIBUTION a diversity of strategies. Some NOT FOR SALE OR DISTRIBUTION microbes obtain energy from organic compounds, whereas others use the energy of the sun or derive their energy from the metabolism of inorganic compounds. The major characteristics of each of the six microbial groups show that each category is distinctive. The popular terms bugs and germs are used in a collective sense,© Jones but there & Bartlett is no basis Learning, for lumping LLC these diverse microbial agents© Jones together. & Bartlett Learning, LLC Further,NOT FOR these SALE terms have OR a DISTRIBUTION negative connotation, because they are usuallyNOT FOR used toSALE OR DISTRIBUTION describe microbial diseases, but it is important to remember that only a handful of microbes are disease producers.

© Jones & Bartlett Learning, LLC ©CHAPTER Jones &2 Bartlett The Microbial Learning, World LLC 45 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

73338_CH02.indd 45 20/11/12 4:20 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONSelf-Evaluation NOT FOR SALE OR DISTRIBUTION

PART I: Choose the single best answer. 1. A major distinction between procaryotic and eucaryotic cells is based on © Jones & Bartlettthe presence Learning, of LLC © Jones & Bartlett Learning, LLC NOT FOR SALE a. a ORcell wall DISTRIBUTION b. DNA c. a nuclear membrane d. NOTa cell membrane FOR SALE OR DISTRIBUTION 2. Most bacteria are considered to be a. harmful b. anaerobes c. autotrophs d. heterotrophs 3. The smallest of these units of measurement is © Jones & Bartlett Learning, a. millimeter LLC b. nanometer c. micrometer© Jones &d. Bartlettcentimeter Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 4. Which of the following are obligate intracellular parasites? a. bacteria b. viruses c. unicellular algae d. diatoms 5. Which one of the following does not have nucleic acid in its structure? © Jones & Bartlett Learning, LLC a. viruses b. diatoms© Jones c. bread & Bartlett mold d. prionsLearning, LLC NOT FOR SALE OR DISTRIBUTION 6. The ﬁ ve-kingdomNOT system FOR of taxonomySALE OR is creditedDISTRIBUTION to a. Haeckel b. Woese c. Whittaker d. Darwin 7. According to Woese, a. Eucarya arose from Archaea. © Jones & Bartlett b. Archaea Learning, arose from LLC Eucarya. © Jones & Bartlett Learning, LLC NOT FOR SALE c. Bacteria, OR DISTRIBUTION Archaea, and Eucarya all arose independently.NOT FOR SALE OR DISTRIBUTION d. None of the above is correct. 8. This bacterium produces an enzyme that catalyzes DNA synthesis. a. E. coli b. Thermus aquaticus c. Serratia marcescens d. Dienococcus © Jones & Bartlett Learning,radiodurans LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION 9. Which of the following microbesNOT are not FOR disease SALE producers? OR DISTRIBUTION a. fungi b. bacteria c. archaea d. protozoa 10. This bacterium produces a red pigment and contaminated communion wafers during a mass in 1263. © Jones & Bartlett Learning, LLC a. Staphylococcus© aureus Jones b. &Serratia Bartlett marcescens Learning, c. Yersinia LLC pestis NOT FOR SALE OR DISTRIBUTION d. Bacillus cereusNOT FOR SALE OR DISTRIBUTION

PART II: Fill in the blank. 1. Bacteria, viruses, fungi, and protozoans are microbes. Name another © Jones & Bartlettgroup that Learning, falls under LLC the microbial umbrella. © Jones & Bartlett Learning, LLC NOT FOR SALE2. The ORcell theory DISTRIBUTION is credited to . NOT FOR SALE OR DISTRIBUTION 3. Compounds of carbon are called compounds. 4. Organisms that do not require organic compounds are called . © Jones & Bartlett Learning, 5. The LLC “energy compound” is called© Jones & Bartlett. Learning, LLC NOT FOR SALE OR DISTRIBUTION 6. Strict anaerobes are killed by NOT FOR SALE. OR DISTRIBUTION 7. The term is used to describe organisms too small to be seen without a microscope.

© Jones &46 Bartlett Learning, LLCPART 1 The Challenge © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

73338_CH02.indd 46 20/11/12 4:20 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE 8OR. DISTRIBUTION are the ancestors of eucaryotes.NOT FOR SALE OR DISTRIBUTION 9. Most bacteria reproduce by . 10. are infectious protein molecules.

PART III: Answer the© Jones following. & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 1. Criticize NOTthe terms FOR bugs SALE and germs OR asDISTRIBUTION used in a collective sense to describe NOT FOR SALE OR DISTRIBUTION microbes. List the categories of microbes, and write a one-sentence description of each. 2. What makes a microbe a microbe? © Jones 3. What & is Bartlett the relevance Learning, to microbiology LLC of Shakespeare’s “What’s© Jones in a name? & Bartlett Learning, LLC NOT FORThat whichSALE we OR call aDISTRIBUTION rose by any other name would smell as sweet.”?NOT FOR SALE OR DISTRIBUTION 4. Heterotrophs are dependent on autotrophs. Why is this the case? 5. The archaea can survive extreme environments. Why? 6. Fungi play a highly signiﬁ cant role as opportunistic pathogens. Deﬁ ne © Jones & Bartlett opportunisticLearning, LLCpathogens and who is most ©susceptible Jones &to Bartlettthese types Learning, of LLC NOT FOR SALE ORinfections. DISTRIBUTION NOT FOR SALE OR DISTRIBUTION 7. Explain why viruses and prions are not cells and are neither prokaryotic nor eukaryotic. 8. Explain why some microbes can survive without oxygen present. 9. Compare© and Jones contrast & eukaryoticBartlett Learning,and prokaryotic LLC cells. © Jones & Bartlett Learning, LLC 10. Why do someNOT bacteria FOR SALEform symbiotic OR DISTRIBUTION partnerships with other life forms? NOT FOR SALE OR DISTRIBUTION

© Jones & Bartlett Learning, LLC ©CHAPTER Jones &2 Bartlett The Microbial Learning, World LLC 47 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

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