Vibrio fischeri BI246 General Microbiology Skidmore College Fall 2011

Classification

Domain: Bacteria; Phylum: Proteobacteria; Class:Gamma Proteobacteria; Order: Vibrionales; family: Vibrionaceae; genus:Vibrio; species: V. fischeri

Description and significance

V. fischeri is a gram negative bacilli bacteria. 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 bacteria is heterotrophic and moves by a flagella. This bacteria is used in research having to do with microbial bioluminescence, quorum sensing for gene expression and bacteria -animal symbiosis.

Genome structure

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 45849 base pairs in length. Chromosome one is 2897536 base pairs long while chromosome two is 1330333 base paris in length.

Cell structure, metabolism & life cycle

V. fischeri is a gram negative bacteria. Therefore, it contains a cytoplasmic membrane, a think peptidoglycan layer, a outer membrane containing lipopolysaccharides. There is also a periplasmic layer and porins which serve as channels through the two membrane layers. This bacteria is oxidase positive since it produces cytochrome C oxidases. The lux operon is responsible for bioluminescence.

Ecology

V. fischeri lives in deep sea marine organisms. It resides in their light organs or in their gut. Ciliated cells within the light organs are able to draw up this bacterium. Therefore, the bacteria begins to colonize the organs and when the organ is completely colonized, the bacteria kills the ciliated cells. Light organs within marine organisms are able to intensify and direct light.

Interesting feature

The symbiosis between V. fischeri and the Hawaiian Bobtail Squid is a very interesting interaction. The bacteria provides bioluminescence in order to help the squid, a nocturnal feeder, to find food because the bacteria is able to eliminate the shadow caused by the moon light. 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 this bacteria in order for it to colonize it's light organs and provide light that eliminates the moonlight for the squid to be effective in acquiring food.