1. The Diversity of Prokaryotic Organisms
Chapter 11

2. Anaerobic Chemotrophs
Found in soil, aquatic environments and the human body
Organisms in this classification
Anaerobic chemolithotrophs
Anaerobic chemoorganotrophs

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. Aerobic Chemolithotrophs
Obtain energy oxidizing reduced inorganic chemicals
Uses oxygen as terminal electron acceptor
Includes sulfur-oxidizing bacteria, nitrifiers and hydrogen-oxidizing bacteria

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. Aerobic Chemoorganotrophs
Obligate aerobes obtain energy using aerobic respiration exclusively
None use fermentation
Characteristic genera include
Micrococcus
Gram-positive cocci found in soil and dust
Produce yellow pigmented colonies
Mycobacterium
Gram-positive bacterium
Live on dead and decaying matter
Pseudomonas
Gram-negative rods
Motile and often pigmented
Common opportunistic pathogen
Thermus and Deinococcus
Both have scientific and commercial uses
Thermus produces Taq polymerase
Dinococcus used to clean up radioactive contamination

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. Archaea that Thrive in Extreme Conditions
Extreme halophiles are found in high salt environments
Salt lakes, soda lakes and brines
Most require 9% salt concentration
Includes genera Halobacterium, Halorubrum, Natronobacterium and Natronococcus
Extreme thermophiles are 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

33. 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