The Diversity of Prokaryotic Organisms Chapter 11 Domains

The Diversity of Prokaryotic Organisms Chapter 11

Domains Bacteria and Archaea • One circular chromosome –not in a membrane • 70 S ribosomes • No membrane-bound organelles • Binary fission –r. RNA provides evidence of phylogenic differences between the 2 Domains

Domain Bacteria • Proteobacteria – Includes most of the gram-negative bacteria – Phylogeny based on r. RNA 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 NH 4+ NO 2– (ammonium to nitrite) • Nitrobacter NO 2– NO 3– (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: H 2 S SO 42– • 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 H 2 S to S 0 – 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: H 7 • 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 H 2 S 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