The Diversity of
Prokaryotic
Organisms
Anaerobic chemotrophs
Anoxygenic phototrophs
Oxygenic phototrophs
Aerobic chemolithotrophs . . . .
Chemoorganotrophs (esp. medically
important ones!)
Prokaryotes
Specifically an anaerobic bacterium
Still many anaerobic habitats (tightly packed soil, polluted
lakes, human body)
First-Ever Scientific Estimate Of Total Bacteria On Earth
Shows Far Greater Numbers Than Ever Known Before:
5 million trillion trillion -- that's a 5 with 30 zeroes
after it (Proceedings of the National Academy of Sciences, 1998)
Bacteria inside all animals combined make up < 1%
of the total amount. By far the greatest numbers
are in the soil and oceans.
Anaerobic Chemoorganotrophs
Using Fermentation
Energy production only by substrate
level phosphorylation. Different
fermentation end products (acids and
gases) for different species
Genus Clostridium - forms endospores
normal flora of GI tract
tetanus
botulism
gas gangrene
Lactic Acid Bacteria
Major fermentation product?
Example genera:
 Streptococcus:
normal throat flora and S.
pyogenes etc.
 Enterococcus: normal GI-tract flora
 Lactobacillus: normal mouth and vagina
flora; food fermentation
Most can grow in aerobic environment but they are
obligate fermenters (hence O2 is of no value!) 
lack catalase (diagnostic use)
Aerobic Chemoorganotrophs:
Obligate Aerobes
Large variety of bacteria; example genera:
 Micrococcus: soil, objects, normal skin flora. E.g.: M.
luteus

Mycobacterium: saprophytes and pathogens – waxy
coat – acid fast, pleomorphic rods – more resistant to
disinfectants and normal drugs
E.g: M. tuberculosis and M. leprae

Pseudomonas: motile gram neg. rods – ubiquitous in
soil and water – mostly harmless, P. aeruginosa is a
opportunistic pathogen – very resistant to disinfectants
and antimicrobial drugs

Thermus (Taq polymerase)
Aerobic Chemoorganotrophs:
Facultative Anaerobes

Corynebacterium: in soil, water, and on plants –
gram pos. pleomorphic rods (“club”) – normal throat
flora, but also C. diphtheriae

Enterobacteriaceae family = enterics =
enterobacteria – what does name tell you? –
includes ~40 genera – if motile: peritrichous flagella

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Enterobacter
Klebsiella
Proteus
E.coli

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Shighella
Salmonella
E.coli
Proteus
Ecophysiology: Thriving in
Terrestrial Environments
Bacteria had to evolve mechanisms to survive
dry spells
Most efficient method: endospore formation
Bacillus and Clostridium species (Position of
endospore is diagnostic)
Streptomyces genus forms conidia at the end
of hyphae (analogous to fungi, but they are
prokaryotes and much smaller than fungi)


Producers of antibiotics (streptomycin,
tetracycline, erythromycin)
S. somaliensis causes actinomycetoma
Animals as Habitats
From arid O2 rich surfaces to moist anaerobic
recesses
Skin

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Staphylococcus aureus
Staphylococcus epidermidis (normal flora)
Both are catalase positive (as opposed to
Strept & enterococcus
Mucous Membrane
Already discussed: Streptococcus in resp. tract. - Lactobacillus
in vagina – Clostridium and enterics in GI tract
Some other genera:
 Bacteroides (30% of bacteria in human feces)
 Campylobacter and Helicobacter (microaerophiles)
 Haemophilus (many normal flora of resp. tract as well as H.
influenza and H. ducreyi)
 Neisseria (normal flora as well as N. gonorrhea and N.
meningitis)
 Mycoplasma: no cell wall – fried egg appearance of culture
colonies – M. pneumoniae
 Treponema and Borrelia: Spriochetes – hard to grow in
culture
Obligate Intracellular Parasites

1.
Cannot reproduce outside a host cell
Rickettsia and Ehrlichia – Transferred by
blood - sucking arthropods

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2.
R. rickettsii: Rocky Mountain spotted fever
R. prowazekii: epidemic typhus
E. chaffeensis : Human ehrlichiosis
Coxsiella - Can form a sporelike
structure

One species: C. burnetii – Q fever – Zoonosis
3. Chlamydia

Person to person transmission

Unique growth cycle
Non-infectious reticulate body reproduces by
binary fission
 Differentiate into infectious elementary body
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Chlamydia cell wall does not contain
peptidoglycan but resembles gram neg.

C. trachomatis, C. pneumoniae