The Diversity of
Prokaryotic Organisms
Chapter 11
Domains Bacteria and Archaea
•One circular chromosome
–not in a membrane
•70S ribosomes
•No membrane-bound organelles
•Binary fission
–rRNA provides evidence of phylogenic
differences between the 2 Domains
Domain Bacteria
• Proteobacteria
– Includes most of the gram-negative bacteria
– Phylogeny based on rRNA studies
– Common photosynthetic ancestor
• few are still photosynthetic
– Mythical Greek god, Proteus
– Largest taxonomic group of bacteria
– Classes designated by Greek letters
The  (alpha) Proteobacteria
•Some grow at low
nutrient levels
•Some have unusual
morphology
•Many are
agriculturally
important
•several medically
important genra
The  (alpha) Proteobacteria
• Human pathogens:
– Bartonella - bacillus
• Cat-scratch disease
• Obligate intracellular parasite:
– Rickettsia – bacillus or coccobacilli
• Arthropod-borne cause spotted fevers
• R. typhi - Endemic murine typhus (fleas)
• R. rickettsii - Rocky Mountain Spotted Fever (ticks)
• Have prosthecae:
– Caulobacter
• Stalked bacteria found in
low nutrient aquatic
environment
•
– Hyphomicrobium
• Budding bacteria found in
low nutrient environment
• Pelagibacter
– Very small with tiny genome
– P. ubique is abundant marine microbe
• Nitrogen-fixing bacteria:
– Azospirillum
• Grows in association with
tropical grasses and sugar
cane
– Rhizobia
• Rhizobium,
Bradyrhizobium
• Infects roots of legumes
forming root nodules
• Nitrifying bacteria :
– Chemoautotrophs
– Oxidize nitrogen
• Nitrosomonas NH4+  NO2– (ammonium to nitrite)
• Nitrobacter NO2–  NO3– (nitrite to nitrate)
• Plant pathogen:
– Agrobacterium
• Inserts plasmid
into plant cells,
inducing tumors
• Crown gall
• Produce acetic acid from ethyl alcohol:
– Acetobacter
– Gluconobacter
• Wolbachia
– Most common
infectious bacteria
– Endosymbionts of
insects and other
animals
The  (beta) Proteobacteria
•Utilize nutrients diffusing
from areas of decomposition
of organic matter
•hydrogen gas, ammonia,
and methane
• Thiobacillus
– Chemoautotroph, oxidizes sulfur: H2S  SO42–
•Sphaerotilus
- hollow sheath
- polar flagella
- problem in sewage
• Spirillum
– Large, aerobic freshwater
bacterium
• Neisseria
– N. meningitidis
• Meningococcal meningitis
– N. gonorrhoeae
• Bordetella
– Aerobic, rods or coccobacillus
– B. pertussis - whooping cough
The  (gamma) Proteobacteria
•Largest subgroup
•Great variety of physiological types
•Includes the enterics
• Beggiatoa
– Chemoautotroph, oxidize H2S to S0
– Gliding motility
– Beggiatoa alba is only species
• Azotobacter and Azomonas
– Nitrogen fixing, free-living soil bacteria
– Large ovoid cell with heavy capsule
• Francisella
– Pleomorphic
– Francisella tularensis – tularemia (rabbit fever)
• Resistant to many antibiotics
• Pseudomonas
–
–
–
–
–
–
Aerobic rods; Polar flagella
Extra-cellular and/or florescent pigments
Opportunistic pathogen
Metabolize wide variety of substrates
Resistant to many anti-microbials
Denitrification
• Legionella
– Found in streams, warm-water
pipes, cooling towers
– L. pneumophilia
• Causes a form of pneumonia
called legionellosis
• Survive inside aquatic amoeba
• Coxiella
– Coxiella burnetii
• Q fever
• Obligate intracellular pathogen
• transmitted via aerosols or milk
• Resistant spore–like body
• Vibrio
– Facultative anaerobic vibrio
– Vibrio cholerae
• Cholera
• Dysentery
– V. parahaemolyticus
• Less severe gastroenteritis
• Undercooked shellfish
• Pasteurella
–
–
–
–
mainly pathogens of domestic animals
Cause pneumonia and septicemia
passed to humans from cat and dog bites
P. multocidia - carried by Komodo dragon
• Haemophilus
– inhabit mucous membranes of upper respiratory tract,
mouth, vagina, and intestinal tract
– require heme fraction (X factor) and NAD cofactor (V
factor)
– H. ducreyi
• Chancroid (STD)
– H. influenzae
• meningitis, pneumonia, bronchitis, septic arthritis,
earaches
• Enterobacteriales (enterics):
•
•
•
•
Facultatively anaerobic, rods
Peritrichous flagella
Most ferment glucose and other sugars
Inhabit intestinal tract of animals (humans)
Enterics
• Escherichia
– Coliforms – fecal contamination
– UTI and Travelers Diarrhea
– Food poisoning – E. coli 0157:H7
• Salmonella
– S. enterica – 2400 servors
– S. enterica servor typhi – typhoid fever
Enterics
• Shigella
– Shigellosis (bacillary dysentery)
• Klebsiella
– K. pneumoniae – serious form of pneumonia
– Some species fix nitrogen
Enterics
• Yersinia
– Y. pestis – plague
• Proteus
– Swarmer cells
– UTI and wound infections
The  (delta) Proteobacteria
•Some species are predators on other bacteria
•Important contributors to the sulfur cycle
• Bdellovibrio
– Aerobic, rod with polar flagella
– attack other gram (-) bacteria similar to the
way a virus would
• Desulfovibrio
– Human intestinal tract and anaerobic sediments
– obligate anaerobe, sulfur reducing bacteria
– Use S for final electron acceptor
– Release tons of H2S annually
• Myxococcus
– Gliding motility
– Feed on bacteria they
encounter
– Cells aggregate to form
fruiting body loaded with
myxospores
The  (epsilon) Proteobacteria
•Microaerophilic, helical or vibrioid rods
•Motile by means of flagella
– Campylobacter
• C. fetus
– causes spontaneous
abortion in domestic
animals
• C. jejuni
– leading cause of
bacterial diarrhea
– Helicobacter
• H. pylori
– common cause of
stomach ulcers