Vibrio fischeri BI246 General Microbiology Skidmore College Fall 2011
Class: Gamma Proteobacteria
Species: V. fischeri
Description and significance
V. fischeri is a gram- negative bacilli bacterium. It is found in marine environments all over the world. It contains bioluminescent properties and lives in symbiosis with many marine animals such as Euprymna scolopies (Hawaiian Bobtail Squid), sepiolidae squid and pinecone fish. This bacterium is heterotrophic and moves by a flagella. This bacterium is used in research having to do with microbial bioluminescence, quorum sensing for gene expression, and bacteria -animal symbiosis.
The strain ES114 of Vibrio fischeri is 4.25Mb. The genome is completely sequenced and it contains a plasmid and two circular chromosomes. The plasmid pES100 is 45,849 base pairs in length. Chromosome one is 2,897,536 base pairs long while chromosome two is 1,330,333 base pairs in length.
Cell structure, metabolism & life cycle
V. fischeri is a gram-negative bacterium. Therefore, it contains a cytoplasmic membrane, a think peptidoglycan layer, and an outer membrane containing lipopolysaccharides. There is also a periplasmic layer and porins which serve as channels through the two membrane layers. This bacterium is oxidase positive since it produces cytochrome C oxidases. The lux operon is responsible for bioluminescence.
V. fischeri lives in deep-sea marine organisms. Bacteria reside in the organism’s light organs or in the gut. Ciliated cells within the light organs are able to draw up this bacterium from the aqueous environment. Therefore, the bacteria begin to colonize the organs and when the organ is completely colonized, the bacteria kill the ciliated cells. Light organs within marine organisms are able to intensify and direct light.
The symbiosis between V. fischeri and the Hawaiian Bobtail Squid is a very interesting interaction. The bacteria provide bioluminescence in order to help the squid, a nocturnal feeder, to find food because the bacteria are able to eliminate the shadow caused by the moonlight. Also, the squid releases almost 95% of the bacteria's population into the water in able for other squid to pick up the bacteria. Each squid must take up these bacteria in order for it to colonize its light organs and provide light that eliminates the moonlight for the squid to be effective in acquiring food.
Doino, J.A., and M. J. McFall-Ngai. 1995. A transient exposure to symbiosis-competent bacteria induces light-organ morphogenesis in the host squid. Biol. Bull. 189:347-355.
Fidopiastis PM, Miyamoto CM, Jobling MG, Meighen EA, Ruby EG. 2002. LitR, a new transcriptional activator in Vibrio fischeri, regulates luminescence and symbiotic light organ colonization. Mol. Microbiol. 45:131-43.
Ruby, E. G. and M. Urbanowski. 2004. Complete genome sequence of Vibrio fischeri: A symbiotic bacterium with pathogenic congeners. PNAS 102: 3004-3009.
"V. Fischeri." Strain Info. Genomic Standards Consortium, n.d. Web. 25 Oct. 2011. <http://www.straininfo.net/genomes/12986>.