Bacterial Diversity

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Chapter 12

• Bacterial Diversity

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Phylum 1 Proteobacteria

• Gram-negative.
• Show extreme metabolic diversity.
• Represent the majority of known gram-negative
  bacteria of medical, industrial, and agricultural
  significance.
• Ex. Escherichia, Neisseria, Nitrosomonas,
  Acetobacter

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Purple Phototrophic Bacteria

• Ex. Rhodospirillum
• Carry out anoxygenic photosynthesis.
• Contain bacteriochlorophylls and carotenoid
• Include the purple sulfur bacteria, which utilize
  H2S as the e- donor for CO2 reduction, and the
  purple nonsulfur bacteria, which are actually
  able to use sulfide as an e- donor for the
  reduction of CO2, but it is toxic at levels
  tolerable by the purple sulfur bacteria.

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Examples of Proteobacteria

• Nitrifying Bacateria Nitrosomonas, Nitrobacter.
• Sulfur- and Iron-Oxidizing Bacteria ex.
  Thiobacillus, Beggiatoa
• Hydrogen-Oxidizing Bacteria ex. Alcaligenes
• Methanotrophs and Methylotrophs Methylomonas,
  Methylobacter
• Pseudomonas and the Pseudomonads some are
  pathogenic, ex. Pseudomonas aeruginosa UTIs and
  URIs.

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Examples of Proteobacteria (cont.)

• Free-Living Aerobic Nitrogen-Fixing Bacteria
  Azotobacter, Azomonas.
• Neisseria, Chromobacterium, and Relatives
  Neisseria coccobacilli, ex. Neisseria
  gonorrhoeae ? gonorrhea.
• Enteric Bacteria Escherichia, Salmonella,
  Proteus, Enterobacter all are gram-neg.,
  nonsporulating rods, nonmotile or motile by
  peritrichous flagella, facultative aerobes,
  relatively simple nutritional requirements, many
  are pathogenic to humans, animals, or plants, or
  are of industrial importance.

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Examples of Proteobacteria (cont.)

• Rickettsias most are obligate intracellular
  parasites, cause for ex. spotted fever, typhus, Q
  fever.
• Gliding Myxobacteria exhibit gliding motility,
  some form multicellular fruiting bodies.

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Phylum 2 Gram-Positive Bacteria

• 2 major phylogenetic subdivisions low GC and
  high GC.
• Low GC, no endospores ex. Staphylococcus,
  Micrococcus, Streptococcus, Lactobacillus
• Low GC, endospore-forming ex. Bacillus,
  Clostridium (C. botulinum, C. tetani).
• Low GC, cell wall-less ex. Mycoplasma.
• High GC ex. Corynebacterium, Propionibacterium,
  Mycobacterium
• High GC, filamentous Streptomyces ? antibiotics.

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Phylum 3 Cyanobacteria and Prochlorophytes

• Cyanobacteria Oxygenic phototrophs,
  morphologically diverse, contain only chlorophyll
  a (green) and phycobilins (blue) thus their
  blue-green color.
• Some contain gas vesicles or heterocysts.
• Many contain cyanophycin (made of Asp and Arg)
  N storage molecule.
• Prochlorophytes contain chlorophyll a and b,
  but not phycobilins, have a shared common
  ancester of green plant chloroplasts and
  cyanobacteria.

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Phylum 4 Chlamydia

• Obligate intracellular parasites.
• Ex. Chlamydia pneumoniae ? respiratory syndromes,
  Chlamydia tranchomatis ? STD
• Chlamydias are small (1µm they were suspected of
  being viruses) and have the simplest biochemical
  capacities of all known cellular organisms.

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Phylum 5 Planctomyces/Pirellula

• Planctomyces stalked bacteria that lack PG
• Have internal compartments for metabolic
  functions, etc. that closely resemble those of
  the euk. cell.

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Phylum 6 The Verrucomicrobia

• Form cytoplasmic appendages called prostheca.

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Phylum 7 The Flavobacteria

• Genera Bacteroides, Flavobacterium.
• Bacteroides Anaerobic, found in the intestinal
  tract of humans and other animals and are the
  numerically dominant bacteria in the human large
  intestine (1010 1011 cells/g of human feces).
  Some species are pathogenic and are the most
  important anaerobes assoc. with human infections.
• Flavobacterium primarily aquatic, rarely
  pathogenic.

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Phylum 8 The Cytophaga Group

• Obligately aerobic.
• Probably account for much of the cellulose
  digestion that occurs by prok. in oxic
  environments in nature.
• Cytophaga spp. some are pathogenic to fish.
• Flexibacter spp. none identified as pathogens.

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Phylum 9 Green Sulfur Bacteria

• Oxidize H2S as an e- donor, but sulfur produced
  resides outside the cell.
• Most assimilate a few organic compounds in the
  light what is this called?
• Autotrophy by reverse citric acid cycle.
• Some form tight 2-membered mutually beneficial
  assoc. with a chemoorganotrophic bacterium called
  consortia.
• Contain various pigments.

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Phylum 10 The Spirochetes

• Gram neg., motile, tightly coiled.
• Treponema commensals or parasites of humans and
  animals, ex. Treponema pallidum ? syphilis.
• Leptospira some are parasitic to humans and
  animals.
• Borrelia most are animal or human pathogens,
  ex. Borrelia burgdorferi ? Lyme disease.

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Phylum 11 Deinococci

• Ex. Deinococcus radiodurans structurally
  complex CW, aerobic chemoorganotroph, highly
  resistant to radiation (more so than endospores)
  and desiccation, have powerful DNA repair
  machinery.
• Thermus aquaticus thermophilic chemoorganotroph
  that produces the Taq polymerase, which is heat
  stable and used for PCR.

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Phylum 12 The Green Nonsulfur Bacteria

• Ex. Chloroflexus filamentous, form thick
  microbial mats in neutral to alkaline hot
  springs, may have first evolved a photosynthetic
  rxn. Center, is the most phylogenetically ancient
  of anoxygenic phototrophs.
• Some have interesting membrane lipids and lack PG.

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Phylum 13 and 14 Deeply Branching
Hyperthermophilic Bacteria

• Hyperthermophiles (optimal growth at temps. above
  80C).
• Ex. Thermodesulfobacterium most thermophilic of
  all sulfate-reducing Bacteria, contain
  ether-linked lipids.
• Ex. Aquifex most thermophilic of all known
  Bacteria. (grow up to 95C, optimum 85C).

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Phylum 15 and 16 Nitrospira and Deferribacter

• Not much is known about these phyla they have
  been identified by rRNA sequencing and are either
  chemolithotrophs or chemoorganotrophs and are
  mesophiles to thermophiles.
• Some Nitrospira ox. nitrite to nitrate.