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



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
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
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
 Can extract residual energy from waste product
of other organisms
Anoxygenic Phototrophs
 Anoxygenic phototrophs oxidize hydrogen
sulfide 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


Prefer to use organic source of electrons in
production of reducing power


Moist soil, bogs and paddy fields
Distinguishes them from purple sulfur bacteria
Remarkably diverse metabolism

Most can grow aerobically and in absence of light
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
 Nitrogen fixation
 Some organisms single celled
 Form multicellular
associations called trichomes
Oxygenic Phototrophs
 Nitrogen-fixing
cyanobacteria

Important ecologically
 Can incorporate both
nitrogen gas and
carbon dioxide into
organic material
 Supports growth of
other organisms
 Helps control
atmospheric carbon
dioxide
heterocyst
 Fixation occurs in thick-
walled heterocyst
 Protects the break
down of nitrogenase
from oxygen
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
Aerobic Chemolithotrophs
 Unicellular sulfur oxidizers found in both
terrestrial and aquatic environments
 Responsible for bioleaching through oxidation
of metal sulfides producing sulfuric acid 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
matter
 None use fermentation
 Characteristic genera include


Pseudomonas
Gram-negative rods
 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
Micrococcus





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
 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
Bioluminescent bacteria
establish relationships with
other animals for food and
protection
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



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


Significant component of skin flora
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
environments


Salt lakes, soda lakes
and brines
 Most require 9% salt
concentration
Includes genera
Halobacterium,
Halorubrum,
Natronobacterium and
Natronococcus
found in regions of volcanic
and thermal vents as well as
sulfurous fissures and hot
springs



Methanothermus grows at
temperatures as high as 97°C
Pyrolobus fumarii grows
between 90°C and 113°C
Sulfolobus species grow only
above 50°C
 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