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

• 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

Domain Bacteria

The (alpha) Proteobacteria

•Some grow at low nutrient levels

•Some have unusual morphology

•Many are agriculturally important

•several medically important genra

• Human pathogens:

– Bartonella - bacillus • Cat-scratch disease

The (alpha) Proteobacteria

• 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 SO4

2–

•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

• Shigella– Shigellosis (bacillary dysentery)

• Klebsiella – K. pneumoniae – serious form of pneumonia

– Some species fix nitrogen

Enterics

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