Prokaryotes

1. Prokaryotes Chapter 27

2. Where Are We Going? • Adaptations of prokaryotes • Diversity of prokaryotes • Ecological Impact of prokaryotes • Importance to humans

3. Organismal Domains Prokaryotes Eukaryotes • 1-5 um in size (10 fold diff.) • 10X’s more biomass • Wider range of environments • Greater diversity • Single, circular chromosome • Best known as bacteria • Disease causing agents are pathogens • Can live without the other • 10-100 um in size • Membrane bound nucleus and organelles • DNA arranged on multiple chromosomes • Can’t live without prokaryotes

4. Gram Staining • Medicinally used to determine type of bacteria causing infection • Bacteria can be gram (+) or gram (-) • (+) simple walls with thicker peptidoglycan, sugar polymer joined by polypeptides • (-) more complex walls with less peptidoglycan and lipopolysaccharide outer layer • Make them more threatening, toxic, and resistant to antibiotics which prevent synthesis of peptidoglycan which inhibits cell wall growth

5. External Prokaryotic Adaptations • Cell wall (previously discussed) • Come in a variety of shapes • Multiple methods for adhesion • Capsule: polysaccharide or protein • Fimbriae: hair-like protein structures • Sex pili: pull cells together before DNA transfer

6. Prokaryote Adaptations • Motility • Directional movement often made possible by flagella • Exhibit taxis, movement to or from a stimuli • Internal organization • Simpler than eukaryotes = no organelles • 1/1000 as much DNA in the nucleoid region • Accessory rings of DNA or plasmids • Reproduction and adaptation • Reproduce asexually by binary fission • Can form endospores when conditions unfavorable • Water removed and metabolism halts

7. Genetic Diversity in Prokaryotes • Exhibit wide range of adaptations and variation • 3 factors determine • Rapid reproduction • Reproduce by binary fission, not sexually • Most offspring identical, some changes likely • Mutation • Rare for a particular gene • Genetic recombination • Transformation, transduction, and conjugation • Combine 1st two and get genetic diversity and rapid evolution • Fit individuals survive and reproduce more prolifically than less fit

8. Transformation • Genotype (some phenotype) altered by uptake of foreign DNA • Harmless strains transformed to virulent when placed in dead virulent cell medium • Forms a recombinant cell • Frederick Griffith experiment from 2107

9. Transduction • Bacteriophages carry bacterial genes from one host to another • Lack machinery to be able to reproduce • Infect bacteria (1) and incorporate their DNA into new bacteriophages • Bacteriophages that result then repeat with new mixed DNA

10. Conjugation • Genetic material transferred between 2 connected cells • Sex pili form bridge • One way process • Often is beneficial • Antibiotic resistance or other tolerance

11. Nutritional Adaptations Prokaryotes categorized based on how energy and carbon are obtained Gr: plants and algae Ylw: certain prokaryotes Pur: marine prokaryotes and halophiles Bl: most prokaryotes, protists, fungi, animals, and some plants

12. Prokaryotic Metabolism • Oxygen • Obligate aerobes use O2 for cellular respiration • Obligate anaerobes are poisoned by O2 • Use fermentation or anaerobic respiration • Facultative anaerobes use O2 if present, but can use alternate methods • Nitrogen • Eukaryotes limited in available nitrogen • Prokaryotes use nitrogen fixation toconvert N2 (nitrogen gas) to NH3 (ammonia) • Necessary to produce AA’s • Increases nitrogen for plant usage

13. Biofilms • Secrete signaling molecules to recruit nearby cells and grow • Produce proteins to stick to self and substrates • Nutrients in and wastes out via channels • Dental plaque below is an example

14. Prokaryotic Diversity

15. Archaea • Live where other organisms can’t survive • Extreme halophiles • Salt environments • E.g Great Salt Lake, Dead Sea, or seawater evaporating ponds • Extreme thermophiles • Very hot water • E.g ocean vents, or acidic conditions • Methanogens • Anaerobic environments with methane as a waste product • E.g. swamps and GI tracts of animals

16. Proteobacteria • Gram-negative • Both aerobic and anaerobic species • 5 subgroups • Alpha: Live in root nodules to fix atmospheric nitrogen • Beta: Nitrogen cycling • Gamma: Photosynthetic and inhabit animal intestines • E.g Salmonella, Vibrio cholerae, and Escheria coliDelta: • Delta: Can form fruiting bodies for selves when food is scarce and attack other bacteria • E.g myxobacteria and Bdellovibrios • Epsilon: pathogenic to humans or other animals • E.g Campylobacter and Helicobacter pylori

17. Other Prokaryotes • Chlamydias • Only survive within animal cells • Gram (-), but lack peptidoglycan • Spirochetes • Spiral through environments by rotating internal filaments • E.gTreponemapallidum(syphilis) and Borreliaburgdorferi(Lyme disease) • Cyanobacteria • Oxygen-generating photosynthesis (only bacteria) • Food for freshwater and marine ecosystems

18. Gram-Positive Bacteria • Actinomycetes • 2 species responsible for tuberculosis and leprosy • Most are free-living decomposers, leave ‘earthy’ odor of soil • Streptomyces • Cultured as sources of antibiotics • Bacillus anthracis • Forms endospores • Clostridium botulinum • Staphylococcus • Streptococcus • Mycoplasmas • Lack cell walls and are tiniest cells • Free-living soil bacteria, but some are pathogens

19. Ecological Interactions • Central role in symbiosis, where 2 species live close • Formed between larger host organism and themselves (symbiont) • Types of interactions can vary • Mutualism • both species benefit • Commensalism • one species benefits while other is unchanged • Parasitism • parasite eats cellular components • Usually harm, but not kill • Pathogens are the parsites that cause disease

20. Bacterial Poisons • Exotoxins are proteins secreted by bacteria • Can exist in the bacteria or without • Vibrio cholerae releases Cl- to gut and water follows • Clostridium tetani produces muscle spasms (lockjaw) • Staphylococcus aureus common on skin and in nasal passages • Produces several types causing varying problems • Acquired from genetic transfer between species • E. coli benign resident of intestines • Acquires genes that produce harmful effects • Endotoxins are components of gram (-) outer membranes • Released when cell dies or digested by defensive cell • Cause same general symptoms • Neisseria meningitidis (bacterial meningitis) and Salmonella (typhoid fever)

21. Research and Technology • Convert milk into cheese and yogurt • Principle agents in bioremediation • Use organisms to remove pollutants • Oil clean up • Sewage treatment • Solid sludge from filters added to anaerobe colonies • Transformed into use for fertilizer or landfill • Liquid waste over biofilms remove organic material