The Bacteria

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The Bacteria
Phylogenetic tree of the major lineages of
Bacteria based on 16S ribosomal RNA Sequence
comparisons
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Kingdom I Proteobacteria

• Purple Phototrophic Bacteria
• The Nitrifying Bacteria
• Sulfur- and Iron-Oxidizing Bacteria
• Methanotrophs and Methylotrophs
• Pseudomonas and Pseudomonads
• Acetic Acid Bacteria
• Free-Living Aerobic Nitrogen-Fixing Bacteria
• Neisseria, Chromobacterium, and Relatives
• Enteric Bacteria
• Vibrio and Photobacterium
• Rickettsia
• Spirilla
• Sheathed Protesbacteria Sphaerotilus and
  Leptothrix
• Budding and Prosthecate/Stalked Bacteria
• Gliding Myxobacteria
• Sulfate- and Sulfur-Reducing Proteobacteria

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The Purple Bacteria, also called Proteobacteria
is the largest and most physiological diverse of
all bacteria
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Purple and Green (Anoxygenic Phototrophic)
Bacteria

• Purple Bacteria
• Bacteriochlorophylls a, b
• Anoxygenic photosynthesis
• One photosystem
• Green Bacteria
• Bacteriochlorophylls c, d or e
• Anoxygenic photosynthesis
• One photosystem
• Cyanobacteria
• Bacteriochlorophyll a
• Oxygenic photosynthesis
• Two photosystems

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Purple and Green (Anoxygenic Phototrophic)
BacteriaBacteriochlorophylls

• Bacteriochlorophylls differ in substituents on
  various parts of the porphyrin ring
• The various modifications lead to changes in the
  absorption spectra of the bacteriochlorophylls
• From the long-wavelength maximum, the
  identification of the bacteriochlorophyll can be
  made.

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Purple and Green (Anoxygenic Phototrophic)
BacteriaClassification

• Anoxygenic phototrophic bacteria are classified
  based on their bacteriochlorophylls and
  photosynthetic membrane systems into three major
  groups
• Purple Bacteria (Nonsulfur purple, Purple sulfur
  bacteria)
• Green Bacteria (Green sulfur, green nonsulfur
  bacteria)
• Heliobacteria
• Anoxygenic phototrophic bacteria also produce
  carotenoid pigments. Therefore, the colors of the
  bacteria are the combination of
  bacterio-chlorophylls and carotenoid pigments

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Purple and Green (Anoxygenic Phototrophic)
BacteriaClassification
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Purple and Green (Anoxygenic Phototrophic)
BacteriaCarotenoids
Carotenoid-less mutant, the actual Bchl a color
Carotenoid-less mutant
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Purple and Green (Anoxygenic Phototrophic)
BacteriaPhotosynthetic Membrane Systems
Differences between green and purple bacteria in
the Photosynthetic Membrane Systems In purple
bacteria photosynthetic pigments are parts of
the internal membane (lamellae). In green
bacteria photosynthetic apparatus consists of a
series of cylindrically shaped structures
called chlorosomes underlaying and attached to
the cytoplasmic membrane. In heliobacteria
bacteriochlorophyll is associated with the
cytoplasmic membrane
Heliobacteria
Purple bacteria
Green Bacteria
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Purple and Green (Anoxygenic Phototrophic)
BacteriaNonsulfur purple bacteria

• can only used sulfide at a low concentration
• have great photoheterotrophic abilities
• some have ability to utilize methanol as sole
  carbon source for phototrophic growth
• most are active N2 fixers.

Rhodospirilum fulvum
Rhodopseudomonas acidophila
Rhodopila globiformis
Rhodocyclus purpureus
Rhodomicrobium vannielii
Rhodobacter sphaeroides
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Purple and Green (Anoxygenic Phototrophic)
BacteriaPurple sulfur bacteria

• deposit sulfur and oxidize it to sulfate,
• commonly found in anoxic zones of lakes as well
  as in sulfur springs,
• Ectothiorhodospira deposits sulfur externally,
  grows halophilically and at high pH, found in
  saline lakes, saltern, and bodies of water high
  in salt,
• limited ability to utilize organic compounds as C
  source for phototrophic growth
• Thiocapsa grows chemoorganotrophically on acetate

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Purple and Green (Anoxygenic Phototrophic)
BacteriaPurple sulfur bacteria
Thiospirillum jenense
Chromatium okenii
Thiocapsa
Thiopedia rosea
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Chemolithotrophs Nitrifying Bacteria

• Bacteria able to grow chemolithotrophically at
  the expense of reduced inorganic nitrogen
  compounds
• (1) Nitrosifying bacteria
• NH3 O2 NO2- H H2O
• (2) Nitrifying bacteria
• NO2- O2 NO3-
• No chemolithotroph is known that will carry out
  the complete oxidation of ammonia to nitrate
• (1) Nitrosomonas, Nitrosococcus, Nitrosospira
• (2) Nitrobacter, Nitrospira, Nitrococcus
• They are members of the purple bacteria

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Chemolithotrophs Sulfur- and Iron-Oxidizing
Bacteria

• Members of purple bacteria
• Have ability to grow chemolithotrophically on
  reduced sulfur compounds
• Only six genera Thiobacillus, Thiosphaera,
  Thiomicrospira, Thermothrix, Beggiatoa and
  Sulfolobus (Archaea) have been cultured.
• Two groups neutrophilic and acidophilic
• The acidophilic group can grow chemolithotrophical
  ly using ferrous iron as electron donor
• Thiobacillus ferrooxidans has been used for
  leaching

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Chemolithotrophs Hydrogen-Oxidizing Bacteria

• Capable of growing with H2 as sole electron donor
  and O2 as electron acceptor,
• Many of them can also grow autotrophically using
  Calvin cycle to fix CO2,
• All contain hydrogenase for binding H2 and use it
  to produce ATP,
• Can grow both chemoorganotrophs and
  chemolithotrophs,
• Most are obligate aerobes, but prefer
  microaerobic conditions when growing
  chemolithotrophically on H2,
• Some can grow on CO,
• Best studied Alcaligenes eutrophus, or Ralstonia
  eutropha

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Methanotrophs and Methylotrophs

• Methanotrophs
• utilize methane, and/or a few other one-carbon
  compounds as sole source of carbon
• aerobes (Purple Bacteria)
• widespread in nature in soil and water
• possess methane monooxygenase
• obligate C1 utilizers
• contain large amount of sterols in internal
  membrane
• Methylotrophs
• utilize methane and other one-carbon compounds as
  electron donors for energy generation and as sole
  sources of carbon
• many can utilize organic acids, ethanols and
  sugars

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Methanotrophs and MethylotrophsClassification

• Based on internal cell structure and carbon
  assimilation pathway
• Type I ribulose monophosphate cycle, lack a
  complete TCA cycle
• Type II Serin pathway

Methylosinus, Type II
Methylococcus capsulatus, Type I
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Methanotrophic Symbionts of Animals

• Intact mussels as well as isolated mussel gill
  tissue consume methane at high rates in the
  presence of O2 due to symbiotic methanotrophic
  bacteria presence.

Symbiotic methanotrophs in the gill tissue of a
marine mussel living near hydrocarbon seeps in
the Gulf of Mexico
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Kingdom VII Green Sulfur Bacteria

• Chlorobium
• Other Green Sulfur Bacteria

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Purple and Green (Anoxygenic Phototrophic)
BacteriaGreen sulfur bacteria

• Morphologically diverse (nonmotile rods, spirals,
  spheres, motile filamentous gliding, prosthecae)
• Some living planktonically in lakes possess gas
  vesicles
• Strictly anaerobic
• Obligate phototrophic
• Most can assimilate simple organic substances
  (aetate, propionate, pyruvate and lactate)for
  phototrophic growth provided that a reduced
  sulfur compound is present as a sulfur source

Chlorobium limicola
Pelodictyron clathratiforme
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Kingdom X The Green Nonsulfur Bacteria

• Chloroflexus
• Heliothrix

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Purple and Green (Anoxygenic Phototrophic)
BacteriaGreen nonsulfur bacteria

• Chloroflexus has been given the designation green
  nonsulfur bacterium
• able to grow chemoorganotrophically in the dark
  under aerobic conditions
• able to grow phototrophically on a wide variety
  of sugars, amino acids, and organic acids
• able to grow phototrophically with H2S or H2 and
  CO2
• best grow photoheterotrophically

Oscillochloris
Oscillochloris
Chloroflexus aurantiacus
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Purple and Green (Anoxygenic Phototrophic)
BacteriaHeliobacteria

• Phylogenetically separate group of anoxygenic
  phototrophic bacteria that contain
  bacteriochlorophyll g
• Consisting of
• Heliobacterium
• Heliophilum
• Heliobacillus
• Strictly anaerobic phototrophs
• Unable to grow by respiratory means
• Similarity between Bchl g and Chlorophyll a
  (modified form of hydroxychlorophyll a)

Heliobacillus mobilis
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Purple and Green (Anoxygenic Phototrophic)
BacteriaA Comparison of electron flow in green
sulfur, heliobacteria and purple bacteria
Bchl g
Bchl a
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Purple and Green (Anoxygenic Phototrophic)
BacteriaEcology
Purple sulfur bacteria from a stratified lake
Green sulfur bacteria from a stratified lake
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Purple and Green (Anoxygenic Phototrophic)
BacteriaEcology
Membrane filters through which were passed
water samples taken at varying depth
Vertical stratification of purple sulfur bacteria
(Amoebabacter purpureus in a CanadianLake
The phototrophic bacterium forms a layer just at
the top of the anoxic zone
A syringe sampling device that can collect water
at intervals
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Purple and Green (Anoxygenic Phototrophic)
BacteriaEcology
Cross-section through a bacterial mat top
cyanobacteria pink phototrophic purple sulfur
bacteria black sulfate-reducing bacteria peach
Bchl b containing cells of Thiocapsa
Massive accumulation of purple sulfur bacteria
Thiopedia roseopersicinia in a spring in Madison.
The green color is from cells of alga Spirogyra
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Kingdom III Cyanobacteria, Prochlorophytes and
Chloroplasts
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Cyanobacteria Diversity

• A large and heterogeneous group of phototrophic
  bacteria
• Oxygenic phototrophs, Bergeys Manual has divided
  them into 5 major groups
• Contain unsaturated fatty acids with two or more
  double bonds instead of one in other bacteria.

Filamentous heterocystous Anabaena
Unicellular Gloeothece
Filamentous, Oscillatoria
Similar to gram-positive bacteria. All
cyanobacteria have chlorophyll a All have
biliprotein pigments Phycobilins, or
Phycoerythrin
Colonial Dermocarpa
Filamentous branching Fischerella
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CyanobacteriaStructural variations gas vesicles
and heterocysts

• Gas vesicles provide flotation, so the cells
  will remain where there is most light.
• Heterocysts rounded, distributed regularly along
  a filament or at one end of a filament, are the
  sole sites of nitrogen fixation in heterocystous
  cyanobacteria

Heterocysts in cyanobacterium Anabaena
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Prochlorophytes

• Prokaryotic oxygenic phototrophs that contain
  chlorophyll a and b but do not have phycobilins.
• Resemble both cyanobacteria and the plant
  chloroplast.

Filamentous prochlorophyte Prochlorothrix
The first prochlorophyte discovered is
Prochloron, has extensive thylakoid membrane
system similar to chloroplast
Prochlorophytes, cyanobacteria and the plant
chloroplasts share a common ancestor