Bio 103 Lake Tahoe Community College Winter Qtr Instructor: Sue Kloss ______

Prokaryotes - Ch. 27 ______

Put on Cells Alive Website with cam to watch growth of colony Intimate universe video - 1 I. Structural, functional and genetic adaptations contribute to prokaryotic success - There are 2 domains of prokaryotes- Archaea and Bacteria - they can live in nearly every habitat on earth, even habitats to extreme for other organisms - there are more prokaryotes in one handful of soil than all the people who have ever lived - typically 1-5 microns in diameter (most eukaryotic cells are 10-100 microns) - three most common shapes of prokaryotes are coccus (sphere), bacillus (rod), and spirillum (spiral) - enormous genetic diversity A. Cell Surface Structures 1. have a cell wall for shape, protection and prevents bursting in hypotonic env. 2. will plasmolyze in hypertonic environment a. severe water loss inhibits most prokaryotes, which is why foods can be preserved in salt 3. Bacteria cell walls contain peptidoglycan - sugar polymers crosslinked by short polypeptides 4. Archaea cell walls contain variety of polysaccharides and proteins but lack peptidoglycan 5. Gram stain - used on Bacteria (not Archaea) a. stain positive indicates large amount of peptidoglycan and simple walls b. stain negative - less peptidoglycan and structurally more complex; outer membrane has lipopolysaccharides 6. Gram stains are important in medicine. Gram negative bacteria are usually more pathogenic a. lipopolysaccharides are generally toxic, and outer membrane protects these bacteria from immune system and from antibiotics 7. many antibiotics inhibit formation of peptidoglycan, preventing functional cell wall (human cells don’t contain peptidoglycan) 8. cell wall of many prokaryotes is covered by a capsule, sticky layer of polysaccharide or protein a. can adhere to substrate or to colony b. can resist immune system attacks 9. Fimbriae and pili - also for adhering - hairlike strands (fimbriae are more numerous and shorter than pili B. Motility 1. About .5 of all prokaryotes are capable of directional movement a. some can move up to 50x own body length per second b. flagella - may be scattered, at one end, or 2 ends 1. rotary 2. .1 as wide as euk. flagella 3. not covered by plasma membrane 4. may move randomly, or exhibit taxis if heterogeneous env. C. Internal and Genomic Organization 1. simpler than euks, both cellularly and genetically 2. not compartmentalized like euks. 3. Some have infolded membranes for certain metabolic functions (Fig. 27.7) 4. genome is structurally very different from a eukaryotic genome and has .001 as much DNA (on avg) a. usually in a ring formation with few associated proteins b. appears in nucleoid region - cytoplasm is lighter than surroundings in electron micrographs c. typical prokaryotes also have plasmids - ring of DNA with only a few genes 1. plasmid genes provide resistance to antibiotics 2. direct metabolism of rarely encountered nutrients 3. other “contingency” functions 4. replicate independently of chromosome 5. transcription and translation are fundamentallly similar in proks and euks, some exceptions a. prok. ribosomes are smaller and differ in protein and RNA content b. certain antibiotics bind to prokaryotic ribosomes and inhibit protein production, but don’ t act the same way in euks. D. Reproduction and Adaptation 1. can reproduce rapidly in favorable environment 2. grow exponentially in numbers 3. most proks. divide every 1-3 hrs, some every 20 min. a. if reproduction went unchecked, a single bacteria could produce a colony weighing more than earth in 3 days! b. fortunately, nutrient supply is limited, they may be eaten by other organisms, toxic waste products they create poison their environment c. many other microbes who compete with them produce chemicals to slow down reproduction 4. some bacteria can withstand harsh conditions - endospores - when nutrient is absent, water removed, metabolism stops. Can remain alive for centuries. (Fig. 27.9) 5. quick generation and conjugation for exchanging genes allows fast natural selection and evolution II. Great diversity of nutritional and metabolic adaptations have evolved in prokaryotes - more diversity than in euks - photoautotrophs, chemoautotrophs, photoheterotrophs - use light for energy but obtain carbon in organic form (found in a number of marine prokaryotes), chemoheterotrophs - must consume energy and nutrients from surroundings -which of these groups do most eukaryotes fall into? A. Metabolic Relationships to oxygen 1. Obligate aerobes - must have O2 2. Facultative anaerobes - will use O2 if available, but can grow anaerobically by fermentation 3. Obligate anaerobes - poisoned by O2 a. some use fermentation b. others use anaerobic respiration where nitrate or sulfate ions final electron acceptor, not O2 B. Nitrogen metabolism 1. N is essential for amino acids and nucleic acids in all organisms 2. euks are limited in the nitrogenous compounds used, proks are more diverse a. some proks, including cyanobacteria, convert atmospheric N to NH3 - nitrogen fixation b. cells can then incorporate this substance into organic molecules c. N fixing bacteria are the most self sufficient of organisms - require only light, water, CO2, N2 and some minerals to grow C. Metabolic cooperation 1. anabena - specialized cells in a colony - (Fig. 27.10) a. genes for both N fixation and Ps, but only one at a time O2 inactivates enzymes for N fixation b. specialized cells called heterocysts live in the filamentous chains with thick walls to prevent O2 c. these do N fixation, and intercellular junctions are specialized to allow transfer of N in exchange for carbos 2. biofilms are surface coating colonies (fig. 27.11) like dental plaque a. cells in colony secrete substances to recruit nearby cells to grow colony b. cells secrete proteins with sticky adhesive to stick together and to substrate c. channels exist so interior cells can remove waste and get nutrients from outer cells 3. cooperation with other domains a. ball shaped aggregates on the ocean floor contain both methane consuming Archaea and sulfate consuming Bacteria 1. Bacteria suppliescompounds for methane consumption (each year, these Archaea consume 300 billion tons of methane- reduce greenhouse warming) 2. Archaea produce wastes such as H and organic products used by Bacteria III. Molecular systematics is illuminating prokaryotic phylogeny A. lessons from molecular systematics 1. Originally, phenotype was used to classify prokaryotes - shape, colony form, Gram stain, etc. 2. molecular systematics is much more accurate for phylogeny, phenotype for rapid ID medically 3. Diversity is immense - only a small fraction of proks can be cultured in labs, needed for sequencing 4. Norman Pace of U of Colorado in 1980’s found ways to sequence out in the field a. each year, this genetic prospecting adds many new branches to the tree of life b. only 4500 proks species have been fully characterized, c. 10,000 species may be in a handful of soil d. different species can incorporate genes from each other - not possible in most euks 1. genetic makeup of many prok species may actually be mosaics of many other spp. 5. divergence of Bacteria and Archaea very early in tree of life B. Bacteria - vast majority of prokaryotes that people are aware of 1. pathogens - eg- one that causes strep throat 2. beneficials - used to make swiss cheese 3. all modes of nutrition and metabolism C. Archaea - share some traits w/ Bacteria and some with Eukarya (table 27.2) 1. Many unique traits 2. Extremophiles a. Extreme thermophiles 1. Sulfer rich volcanic springs 2. deep sea hydrothermal vents b. halophiles- salt lovers 1. Great Salt Lake (and Mono Lake) and Dead Sea 2. Some spp. tolerate salt, others require it; some form bacteriorhodopsin - purple-red pigment (Fig. 27.14) c. Methanogens use CO2 to oxidize H2, releasing methane as a waste - 1. often strict anaerobes poisoned by O2 2. some spp, in swamps and marshes where all O2 has been consumed (marsh gas) 3. some live in guts of herbivores and termites - essential for nutrition 4. important decomposers in sewage facilities IV. Prokaryotes play crucial roles in the biosphere A. Chemical recycling - all organic molecules have inorganic compounds that were once in soil, air, water 1. proks are major decomposers, returning these compounds to inorganic status 2. proks convert inorganic compounds to forms that can be used by other organisms a. cyanobacteria do Ps and produce O2, others fix N B. Symbiotic relationships 1. symbiosis - orgs living in direct contact - larger is host, smaller is symbiont - there are 10x as many bacterial cells in your body as there are your own cells - bacteria in your gut synthesize many of your nutrients, and also signals your body to produce antimicrobial compounds that don’t affect themselves, and also signals your body to activate genes of your own that build networks of intestinal blood vessels that absorb nutrients a. mutualism - flashlight fish (Fig. 27.15) - both benefit b. parasitism - one benefits, one is harmed c. commensalism - one benefits, one has no impact V. Prokaryotes have both harmful and beneficial impacts on humans A. Pathogenic prokaryotes - a SMALL fraction of all prok species 1. Proks cause about .5 of all human disease a. tuberculosis kills 2 - 3 mil. /yr b. diarrheal diseases kill 2 mil more c. Lyme disease- a bacteria carried by a tick (Fig. 27.16) - affects joints, heart and nervous system 2. Pathogenic proks generally produce toxins which cause the harm a. exotoxins - excreted by the bacteria into your system - cholera and botulism b. endotoxins - lipopolysaccharide components of the outer membrane of gram-neg. bacteria 1. usually harmful only when bacteria dies and cell walls broken down - Salmonella, typhoid fever 3. Used in bioterrorism a. anthrax, botulism and plague B. Prokaryotes in research and technology 1. convert milk to cheese 2. used in biotechnology to grow gene products and transfer genes between plants 3. bioremediation- (Fig. 27.17) remove pollutants from soil, water, air a. sewage is rendered non pathogenic b. break down radioactive wastes c. clean up oil spills d. recover metals from ores - gold from ore, copper from copper sulfides e. “designer prokaryotes” Venter from Human Genome proj hopes to create genetically a prok that can produce large amts. of H2 for use in alt. energy Lesson Objectives Chapter 27 - Prokaryotes

1. Explain why it might be said that the history of life on Earth is one long “age of prokaryotes.” 2. Explain why prokaryotes are unable to grow in very salty or sugary foods, such as cured meats or jam. 3. State the function(s) of each of the following prokaryotic features: a. capsule b. fimbria c. sex pilus d. nucleoid e. plasmid f. endospore . 4. List the three domains of life. 5. Describe the structure, composition, and functions of prokaryotic cell walls. 6. Distinguish the structure and staining properties of gram-positive bacteria from those of gram-negative bacteria. 7. Explain why disease-causing gram-negative bacterial species are generally more deadly than disease-causing gram- positive bacteria. 8. Explain how the organization of prokaryotic genomes differs from that of eukaryotic genomes. 9. Distinguish, with prokaryotic examples, among photoautotrophs, chemoautotrophs, photoheterotrophs, and chemoheterotrophs. 10. Distinguish among obligate aerobes, facultative anaerobes, and obligate anaerobes. 11. Explain the importance of nitrogen fixation to life on Earth. 12. Describe the specializations for nitrogen fixation in the cyanobacterium Anabaena. 13. Explain why some archaea are known as extremophiles. Describe the distinguishing features of methanogens, extreme halophiles, and extreme thermophiles. 14. Describe the mutualistic interaction between humans and Bacteroides thetaiotaomicron, bacteria found in the gut. 15. Define bioremediation. Describe two examples of bioremediation involving prokaryotes.