Lecture 4.12 Notes

Lecture 4.12 Notes - Neisseria, Chromobacterium and...

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Neisseria, Chromobacterium and Relatives Gram-negative cocci Non motile Aerobic metabolism Commensals but include 2 pathogens – N. gonorrhea and N. meningitidis Enteric Bacteria Key genera: Escherichia, Shigella, Salmonalla, Klebsiella, Yersinia Very well characterized group due to close association with human health Homogeneous phylogenetic group (grouping within the γ - proteobacteria) but genera and species are more narrowly defined (see below) and separate genera maintained for practical reasons o classifications more heavily weighted towards phenotypic rather than phylogenetic characteristics. Escherichia nearly universal (but not dominant) intestinal bacteria in humans and other warm bloods interactions can range from pathogenic to mutualistic; o some beneficial ( e.g. – synthesis of vitamins such as vitamin K) o some pathogenicic (e.g. – strain O157:H7) K antigen permits attachment and colonization Enterotoxin(s) cause diarrhea Shigella Strains of Shigella often have 70% genomic hybridization w/ E. coli ; actually same species. Commonly pathogenic in humans cause of bacillary dysentery (gasteroenteritis) Salmonalla ~50% genomic hybridization w/ E. coli nearly all Salmonella species pathogenic Klebsiella Klebsiella pneumoniae – associated with pneumonias in humans Most strains fix N 2 Yersinia Y. enterolitica found in the intestines of most domestic animals food-borne spread and development of life-threatening enteric fever in humans Y. pestis tick-borne cause of bubonic (and pneumonic) plague in humans Vibrio, Aliivibrio and Photobacterium Gram-negative facultatively aerobic rods
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γ -proteobacteria Aquatic habitat Vibrio cholerae – cholera one of most prevalent diseases in underdeveloped countries Vibrio parahaemolyticus – major cause of gasteroenteritis in areas where raw fish is consumed Bioluminescence – not confined to, but often found among, this group o Regulated by quorum sensing o Only occurs in oxic environments (possibly evolved as method of detoxifying O 2 ) Rickettsias Small coccoid or rod-shaped α - proteobacteria Obligate intracellular parasites (w/ 1 exception) Strong phylogenetic association with mitochondria evolved from ancient symbiont? Causative agents of several human diseases o Typhus o Rocky Mountain Spotted Fever o Q Fever Replication in cytoplasm – infection requires metabolic activity of both host and parasite Burst of infected cell to release progeny Metabolism and pathogenesis: highly specific energy metabolism – most species oxidize only glutamine or glutamate and cannot oxidize glucose ( Coxiella burnettii – exception) cannot survive long outside host require insect vector for transmission (w/exception of C. burnettii , which can be spread by aerosols) Rochalimaea is atypical – not obligate intracellular parasite and can be grown in culture
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Lecture 4.12 Notes - Neisseria, Chromobacterium and...

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