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Chapter 11The Prokaryotes

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Prokaryotic TaxonomyProkaryotic Taxonomy

• Prokaryotic genealogical tree– Based on 16S ribosomal RNA– Two domains

• Archaea– Two phyla

• Bacteria– 23 phyla

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Figure 11.1

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Domain Archaea

• A1 Crenarchaeota– One class– Morphologically diverse– Metabolically diverse

• A2 Euryarchaeota– Five classes– Methanogens– Extreme halophiles– Thermoacidophiles

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Domain Bacteria

• B4 Deinococcus-Thermus– Deinococcus radiodurans

• Resistance to radiation

– Thermus aquaticus• Production of Taq polymerase

• B5 Chrysiogenetes– Single species– Anaerobic respiration using arsenate

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Domain Bacteria

• B10 Cyanobacteria– Oxygenic photosynthetic bacteria– Once called blue-green algae (not algae)– Major nitrogen fixer

• Carbon from CO2

• Nitrogen as N2

• Heterocysts– Specialized cells for fixation of nitrogen– Photosynthesis in other cells

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Domain Bacteria

• B11 Chlorobi– Anoxygenic phototrophic bacteria

• Anaerobic environments• Photosynthetic

– Found in deep, clear bodies of water

• B12 Proteobacteria– Largest phylum

• 1300+ species• Alphaproteobacteria class• Betaproteobacteria class• Gammaproteobacteria class• Deltaproteobacteria class• Epsilonproteobacteria class

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Alphaproteobacteria

• Environmentally important genera– Acetobacter

• Production of acetic acid in vinegar

– Agrobacterium• Produce cancerlike disease of plants• Ti plasmids

– Rhizobium and Bradyrhizobium• Symbiotic nitrogen-fixing bacteria• Root nodules of legumes

– Appendaged bacteria• Prosthecate bacteria—found in aquatic environs

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Betaproteobacteria

• Bordetella– B. pertussis—causes whooping cough

• Neisseria– N. meningitidis—meningitis– N. gonorrhoeaea—gonorrhea

• Sheathed bacteria– Tube surrounding bacteria– Contaminated water and sewage treatment

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Gammaproteobacteria

• 13 orders– Enterobactgeriales

• Contain the enteric bacteria• Include human pathogens

– Salmonella typhi– Shigella spp.– Yersinia pestis– Escherichia coli

– Vibrionales• Curved rods

– Vibrio chlerae--cholera

– Pasteurellales• Pasteurella and Haemophilus genera

– Pseudomonales• P. aeruginosa

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Deltaproteobacteria

• Sulfur-reducing bacteria– Sulfates and sulfur to hydrogen sulfide– Mud flats, brackish water– Desulfovibrio spp.

• Black metal sulfides of Black Sea

• Gliding Fruiting bacteria– Myxobacteria– Soil organisms

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Epsilonproteobacteria

• Campylobacter– C. jejuni—diarrheal illness

• Helicobacter– H. pylori—gastric ulcers

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Domain Bacteria

• B13 Firmicutes– Three classes

• Clostridia– Endospore forming

– Strict anaerobes

• Bacilli– Endospore forming

– Aerobic and/or facultative anaerobes

• Mollicutes– Lack cell wall

– Mycoplasmas

– Gram-positive cocci• Spread between Clostridia and Bacilli classes

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Domain Bacteria

• B13 Firmicutes (continued)– Gram-positive cocci

• Arrangement important for identification• Physiological differences

– Staphylococcus» Facultative anaerobes

• Four genera produce lactic acid– Streptococcus spp.– Leuconostoc– Pediococcus– Lactobacillus

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Domain Bacteria

• Actinobacteria– Oddly shaped bacteria

• Arthrobacter genus– Change shape during growth

• Bifidobacterium genus– Irregular branched cells

» Propionibacterium acne» Corynebacterium diptheriae

– Acid-fast• Mycobacterium

– Tuberculosis and Hansen’s disease

• Nocardia

– Spore-forming• Actinomycetes• Abundant in soil

Figure 11.19

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Domain Bacteria

• B16 Chlamydiae– Obligate intracellular parasites– Complicated reproductive cycle

• Reticulate body– vegetative cell– multiplication

• Elementary body– Chlamydiospore– Spread of infection

Figure 11.21

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Domain Bacteria

• B17 Spirochaetes– Helical shape– Corkscrew motility

• Flagella—two axial filaments

– Metabolically diverse– Causes of human disease

• Treponema pallidum—syphilus• Leptospira interrogans—leptospirosis• Borrelia burgdorferi—Lyme’s disease

Figure 11.22

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Domain Bacteria

• B20 Bacteroidetes– Purple nonsulfur bacteria

• Photosynthetic

– Bacteroides• Mouth and intestinal tract

• B21 Fusobacteria– Oral and respiratory systems

• F. periodonticum– dental abscesses

• F. nucleatum– Respiratory system