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The Diversity of Prokaryotic Organisms

The Diversity of Prokaryotic Organisms. Anaerobic chemotrophs Anoxygenic phototrophs Oxygenic phototrophs Aerobic chemolithotrophs . . . . Chemoorganotrophs (esp. medically important ones!). Prokaryotes. Specifically an anaerobic bacterium

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The Diversity of Prokaryotic Organisms

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  1. The Diversity of Prokaryotic Organisms Anaerobic chemotrophs Anoxygenic phototrophs Oxygenic phototrophs Aerobic chemolithotrophs . . . . Chemoorganotrophs (esp. medically important ones!)

  2. Prokaryotes Specifically an anaerobic bacterium Still many anaerobic habitats (tightly packed soil, polluted lakes, human body) First-Ever Scientific Estimate Of Total Bacteria On Earth Shows Far Greater Numbers Than Ever Known Before: 5 million trillion trillion -- that's a 5 with 30 zeroes after it (Proceedings of the National Academy of Sciences, 1998) Bacteria inside all animals combined make up < 1% of the total amount. By far the greatest numbers are in the soil and oceans.

  3. Anaerobic Chemoorganotrophs Using Fermentation Energy production only by substrate level phosphorylation. Different fermentation end products (acids and gases) for different species Genus Clostridium-forms endospores normal flora of GI tract tetanus botulism gas gangrene

  4. Lactic Acid Bacteria Major fermentation product? Example genera: • Streptococcus:normal throat flora and S. pyogenes etc. • Enterococcus: normal GI-tract flora • Lactobacillus: normal mouth and vagina flora; food fermentation Most can grow in aerobic environment but they are obligate fermenters (hence O2 is of no value!)  lack catalase (diagnostic use)

  5. Aerobic Chemoorganotrophs:Obligate Aerobes Large variety of bacteria; example genera: • Micrococcus:soil, objects, normal skin flora. E.g.: M. luteus • Mycobacterium:saprophytes and pathogens – waxy coat – acid fast, pleomorphic rods – more resistant to disinfectants and normal drugsE.g: M. tuberculosis and M. leprae • Pseudomonas: motile gram neg. rods – ubiquitous in soil and water – mostly harmless, P. aeruginosa is a opportunistic pathogen – very resistant to disinfectants and antimicrobial drugs • Thermus (Taq polymerase)

  6. Aerobic Chemoorganotrophs:Facultative Anaerobes • Corynebacterium: in soil, water, and on plants – gram pos. pleomorphic rods (“club”) – normal throat flora, but also C. diphtheriae • Enterobacteriaceaefamily = enterics = enterobacteria – what does name tell you? – includes ~40 genera – if motile: peritrichous flagella • Enterobacter • Klebsiella • Proteus • E.coli • Shighella • Salmonella • E.coli Proteus

  7. Ecophysiology: Thriving in Terrestrial Environments Bacteria had to evolve mechanisms to survive dry spells Most efficient method: endospore formationBacillus and Clostridium species (Position of endospore is diagnostic) Streptomyces genus forms conidiaat the end of hyphae (analogous to fungi, but they are prokaryotes and much smaller than fungi) • Producers of antibiotics (streptomycin, tetracycline, erythromycin) • S. somaliensis causes actinomycetoma

  8. Animals as Habitats From arid O2 rich surfaces to moist anaerobic recesses Skin • Staphylococcus aureus • Staphylococcus epidermidis(normal flora) Both are catalase positive (as opposed to Strept & enterococcus

  9. Mucous Membrane Already discussed: Streptococcus in resp. tract. - Lactobacillus in vagina – Clostridium and enterics in GI tract Some other genera: • Bacteroides (30% of bacteria in human feces) • Campylobacterand Helicobacter(microaerophiles) • Haemophilus (many normal flora of resp. tract as well as H. influenza and H. ducreyi) • Neisseria(normal flora as well as N. gonorrhea and N. meningitis) • Mycoplasma: no cell wall – fried egg appearance of culture colonies – M. pneumoniae • Treponemaand Borrelia: Spriochetes – hard to grow in culture

  10. Obligate Intracellular Parasites • Cannot reproduce outside a host cell • Rickettsia and Ehrlichia – Transferred by blood - sucking arthropods • R. rickettsii: Rocky Mountain spotted fever • R. prowazekii: epidemic typhus • E. chaffeensis : Human ehrlichiosis • Coxsiella - Can form a sporelike structure • One species: C. burnetii – Q fever– Zoonosis

  11. 3. Chlamydia • Person to person transmission • Unique growth cycle • Non-infectious reticulate body reproduces by binary fission • Differentiate into infectious elementary body • Chlamydia cell wall does not contain peptidoglycan but resembles gram neg. • C. trachomatis, C. pneumoniae The End

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