The Diversity of Prokaryotic Organisms

							The Diversity of
Prokaryotic Organisms


      Chapter 11
Anaerobic Chemotrophs
 Found in soil, aquatic environments and the
  human body
 Organisms in this classification
     Anaerobic chemolithotrophs
     Anaerobic chemoorganotrophs
Anaerobic Chemotrophs
 Chemolithotrophs oxidize reduced inorganic
  chemicals to produce energy
     Use alternate terminal electron acceptor other
      that oxygen
          Usually carbon dioxide or sulfur
     Usually members of the domain Archaea
  Anaerobic Chemotrophs
 Methanogens
      Members of Domain Archaea
      Produce energy by reducing
       hydrogen and using carbon
       dioxide as terminal electron
       acceptor(4H2 + CO2 CH4 + 2H2O)
           This process creates
            methane and water
      Commonly found in sewage,
       swamps marine sediments and
       digestive tract of mammals
      Highly sensitive to oxygen
           Anaerobic chambers used for
            cultivation
  Anaerobic Chemotrophs
 Some anaerobic chemoorganotrophs produce
 ATP via anaerobic respiration through the
 oxidation of organic molecules
     Also use terminal electron acceptor other than
      oxygen
          Sulfur and sulfate are common
 Other anaerobic chemoorganotrophs produce
 energy through fermentation
     Produce energy through substrate
      phosphorylation only
Anaerobic Chemotrophs
 Sulfur and sulfate-reducing bacteria use
  sulfur as terminal electron acceptors and
  oxidize organic material
     Reducing it to hydrogen sulfide
          Responsible for rotten egg smell
     These organisms essential for sulfur cycle in
      ecosystem
 Generally found in mud rich in organic matter
  and sulfur
Yellowstone Mud Geyser
Yellowstone Park Mud Pot
Yellowstone Morning Glory Pool
Anaerobic Chemotrophs
 Members of genus Clostridium are Gram-
  positive rods
     Produce endospores
     Common inhabitant of soil
 Organisms in this genus ferment wide variety
  of compounds to produce energy
     Some organisms ferment amino acids in
      process of putrefaction
          the anaerobic decomposition of organic matter by
           bacteria and fungi that results in obnoxiously
           odorous products; rotting.
Anaerobic Chemotrophs
 Lactic acid bacteria are
  Gram-positive organisms
  that produce lactic acid as an
  end product of fermentation
    Includes Streptococcus,
      Enterococcus,
      Lactococcus,
      Lactobacillus,
      Leuconostoc
 Most organisms of this group
  can grow in aerobic
  environments but are
  obligate fermenters
  Anaerobic Chemotrophs
 Propionibacterium species are Gram-positive
  rods
 Organisms produce propionic acid as end
  product of fermentation
     Essential in the production of Swiss cheese
     These organisms can also ferment lactic acid
     Principle bacteria of acne and foot odor
 Can extract residual energy from waste product
  of other organisms
Anoxygenic Phototrophs
 Anoxygenic phototrophs oxidize hydrogen
  sulfide (H2S) or organic molecules when
  making NADPH
 Many organisms inhabit restricted ecological
  niches
     Aquatic habitats such as bogs, lakes and
      upper layers of mud
     Includes purple bacteria and green bacteria
  Anoxygenic Phototrophs
 Purple bacteria
    Gram-negative organisms
    Appear red, orange or purple due
     to pigments used in
     photosynthesis
      Purple sulfur bacteria found
       in habitats such as sulfur
       springs
          Prefer hydrogen sulfide to
           generate reducing power
          Most organisms strict
           anaerobes and
           phototrophs
            Some can grow aerobically
             and in absence of light
Anoxygenic Phototrophs
 Purple non-sulfur bacteria
     Found in variety of aquatic habitats
          Moist soil, bogs and paddy fields
     Prefer to use organic source of electrons in
      production of reducing power
          Distinguishes them from purple sulfur bacteria
     Remarkably diverse metabolism
          Most can grow aerobically and in absence of light
The Great Salt Lake,
Utah

Anaerobic purple sulfur
bacteria found at the
interface of the very salty
(25%) deeper water with
the less salty (5-12 %)
surface water. (Produce H2S)

Shown against the green
phytoplankton of the
surface water. (Use H2S as an
electron source for energy production)
   Anoxygenic Phototrophs
 Green bacteria
   Gram-negative organisms
   Typically green or brown
   Green sulfur bacteria
      Found in habitats similar

       to purple sulfur bacteria
      Use hydrogen sulfide as

       source of electrons
      Many lack flagella but

       have gas vesicles
      All are strict anaerobes
Anoxygenic Phototrophs
 Green non-sulfur bacteria
     Characterized by filamentous growth
     Metabolically resemble purple non-sulfur
      bacteria
          Use organic molecules to generate reducing
           power
     Can grow aerobically and in absence of light
Oxygenic Phototrophs
 Photosynthetic bacteria that use water as
  source of electrons
     Oxidation of water liberates oxygen
     Cyanobacteria thought to be earliest organism
      of group
     Cyanobacteria act as primary producers
          Harvest sunlight to produce organic compounds
           through conversion of carbon dioxide
   Oxygenic Phototrophs
 The cyanobacteria
    Includes more than 60 genera
    Inhabit wide range of
     environments
        Aquatic to terrestrial

    Able to convert nitrogen gas to
     ammonia (NH3)
        Nitrogen fixation

    Some organisms single celled
        Form multicellular
         associations called trichome
            Hair like structures
      Oxygenic Phototrophs
       Nitrogen-fixing
         cyanobacteria
             Important ecologically
                Can incorporate both                        heterocyst
                 nitrogen gas and
                 carbon dioxide into
                 organic material
                     Supports growth of
                                               Fixation occurs in thick-
                      other organisms            walled heterocyst
                     Helps control                Protects the break
                      atmospheric carbon
                      dioxide                       down of nitrogenase
                                                    from oxygen
N2 + 8H+ + 8e− + 16 ATP → 2NH3 + H2 + 16ADP + 16 Pi
Aerobic Chemolithotrophs
 Obtain energy oxidizing reduced inorganic
  chemicals
     Uses oxygen as terminal electron acceptor
     Includes sulfur-oxidizing bacteria, nitrifiers and
      hydrogen-oxidizing bacteria
Aerobic Chemolithotrophs
 Sulfur-oxidizing bacteria are Gram-negative rods or
  spirals
 Grow in filaments
 Obtain energy through oxidation of reduced sulfur
      Including hydrogen sulfide, elemental sulfur and
       thiosulfate
      Molecular oxygen serves as terminal electron acceptor
          This produces sulfuric acid
  Aerobic Chemolithotrophs
 Filamentous sulfur oxidizers
  live in sulfur springs, sewage
  polluted waters and on
  surface of aquatic sediments
 Causes bulking in sewage
  treatment facilities
      Interferes with the separation
       of solid sludge and liquid
       effluent
      Bulking helps water
       treatment but harms sewage
       disposal
Aerobic Chemolithotrophs
 Unicellular sulfur oxidizers found in both
  terrestrial and aquatic environments
 Responsible for bioleaching through oxidation
  of metal sulfides producing sulfuric acid (H2SO4)
  and liquid metal
      Some species produce enough acid to lower
       pH to 1.0
   Aerobic Chemolithotrophs
 Nitrifiers
    Diverse group of Gram-negative bacteria
    Oxidize inorganic nitrogen to obtain energy
        Nitrogen such as ammonia and nitrite

        Important in the breakdown of ammonia containing waste

    Nitrogen polluted waters become hypoxic
        As nitrogen is oxidized oxygen is consumed

    Nitrifiers encompass two metabolically distinctive groups
        Ammonia oxidizers

        Nitrite oxidizers
Aerobic Chemolithotrophs
 Hydrogen-oxidizing bacteria are Gram-
  negative bacteria
 Obligate chemolithotrophs
 Tend to thermophilic
     Found primarily in hot springs
     Some members thrive at 95°C
Aerobic Chemoorganotrophs
 Oxidized organic compounds to obtain
  energy
 Use oxygen as terminal electron acceptor
 Include tremendous variety of organisms
 Chemoorganotrophs can be classified as
     Obligate aerobes
     Facultative anaerobes
   Aerobic Chemoorganotrophs
 Obligate aerobes obtain energy     Mycobacterium
  using aerobic respiration                Gram-positive bacterium
  exclusively                              Live on dead and decaying
    None use fermentation                  matter
                                       Pseudomonas
 Characteristic genera include
                                        Gram-negative rods
    Micrococcus
                                        Motile and often pigmented
          Gram-positive cocci found
                                        Common opportunistic
           in soil and dust              pathogen
          Produce yellow pigmented  Thermus and Deinococcus
           colonies
                                        Both have scientific and
                                         commercial uses
                                                Thermus produces Taq
                                                 polymerase
                                                Dinococcus used to clean
                                                 up radioactive
                                                 contamination
Aerobic Chemoorganotrophs
 Facultative anaerobes preferentially use aerobic
  respiration
      Can use fermentation as alternative in absence of
       oxygen
 Characteristic genera include
    Corynebacterium
       Gram-positive pleomorphic rods

       Inhabit soil, water and surface of
        plants
    Enterobacteriaceae
       Gram-negative rods

       Commonly referred to as enterics

       Reside in intestinal tract
   Thriving in
   Terrestrial Environments
 Numerous genera that inhabit soil can
  form resting stages that enable survival in
  dry periods
 Endospores, cysts, fruiting bodies, and
  mycelium are examples of resting stage
  structures
    Bacillus and Clostridium species
      produce endospores
    Azobactor species produce cysts
    Myxobacteria species form fruiting
      bodies; social aggregations
    Streptomyces species form mycelium
 Endospores tend to be more resistant to
  environmental insult than cysts or fruiting
  bodies
  Thriving in
  Terrestrial Environments
 Bacteria associated with plants
  use different means to obtain
  nutrients
      Agrobacterium produce plant
       tumors to gain nutrient
          These tumors are often fatal to

           plant
      Rhizobium have a mutually
       beneficial relationship with plants
          Organisms fix nitrogen that is

           used for a nutrient source for the
           plant
Thriving in Aquatic Environments
 Organisms produced numerous
  mechanisms for nutrient
  acquisition and retention
    Clustering within a sheath
           Bacteria form chains
            encased in tube which
            enables them to find
            favorable habitat
               Includes genera Sphaerotilus
                and Leptothrix
      Derive nutrient from other
       organisms
           Bdellovibrio prey on other
            organisms Form plaques on
            lawns of other bacteria
           Bioluminescent bacteria
            establish relationships with
            other animals for food and
            protection; Quorum sensing
           Legionella live inside
            protected confines of
            protozoa
   Thriving in
   Aquatic Environments
 Organisms produced numerous
  mechanisms for nutrient
  acquisition and retention
    Move by unusual means
           Spirochetes move via axial
            filaments in corkscrew
            motion
           Magnetotactic bacteria
            move by means of magnetic
            crystals aligning them with
            earth’s magnetism
      Formation of storage
           Spirillum species form
            volutin granules to store
            phosphate
           Certain marine bacteria
            store sulfur and nitrate for
            oxidation and reduction
               Gives advantage to bacteria
                in certain environments
   Animals as Habitats
 Bodies of animals provide wide variety of
  ecological habitats for bacteria
    Skin inhabited by Staphylococcal species
           Significant component of skin flora
      Mucous membranes is inhabited by
       numerous genera including Bacteriods,
       Bifidobacterium, Campylobacter and
       Helicobacter, Neisseria and Treponema
      Bacteria that are obligate intracellular
       parasites including Rickettsia, Orientia and
       Ehrlicia reside in blood sucking arthropods
           Mainly ticks or lice
      Coxiella transmitted person to person
       without arthropod vector
  Archaea that Thrive in
  Extreme Conditions
 Extreme halophiles are  Extreme thermophiles are
  found in high salt              found in regions of volcanic
  environments                    and thermal vents as well as
      Salt lakes, soda lakes     sulfurous fissures and hot
       and brines                 springs
          Most require 9% salt      Methanothermus grows at
           concentration              temperatures as high as 97°C
      Includes genera               Pyrolobus fumarii grows
       Halobacterium,                 between 90°C and 113°C
       Halorubrum,                   Sulfolobus species grow only
       Natronobacterium and           above 50°C
       Natronococcus                     Also require pH between 1
                                          and 6
Archaea that Thrive in
Extreme Conditions
 Thermophilic extreme
  acidophiles grow at
  extremely high temperature
  and low pH
 Two significant genera
    Thermoplasma
           Grow optimally at pH
            of 2
               Some species lyse at
                neutral pH
      Picrophilus
           Optimal growth below
            pH 1