Photobacterium phosphoreum

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Photobacterium phosphoreum
Scientific classification
Kingdom: Bacteria Phylum: Proteobacteria Class: Gammaproteobacteria Order: Vibrionales Family: Vibrionaceae Genus: Photobacterium Species: P. phosphoreum
Binomial name
Photobacterium phosphoreum

Description and significance

Photobacterium phosphoreum is a luminescent bacterium. Its physical characteristics are gram-negative, rod-like shape, plump and large (0.8-1.3 um in diameter and 1.8-2.4 um in length). It can be motile or non-motile. Those that are motile have 1-3 unsheathed polar flagella. Its optimum temperature is 18-25˚C [1]. It emits a blue-green light. It can be cultivated in Long and Hammer Agar (1% NaCl). It is known as a symbiotic bacterium that lives in the light organ of some marine fishes. It can also live freely in seawater, saprophytically and parasitically [2].

Its major significance is its symbiotic relationship with some marine animals like fishes and squids. They have specialized organs that provide P. phosphoreum with a safe place to reside and food; while these animals use the light that the bacteria provide for camouflage and even for attracting mates or escape from predators. Another role that P. phosphoreum has is the ability of signaling the relative toxicity of a substance due to the connection of the light producing process with the cellular metabolism. If the toxins disrupt the cellular metabolism, then the strength of the light produced decreases.

Cell structure and metabolism

P. phosphoreum is a chemoorganotroph which is capable of respiratory and fermentative metabolism [3]. It is a facultative anaerobe that can grow in the absence of oxygen when appropriate electron-acceptors are present. It doesn’t denitrify; in other word, it cannot use nitrogen molecules [4].

Ecology

P. phosphoreum is mostly considered a marine bacterium because sodium ions are required for its growth. It lives in the depth of the ocean, seawater, marine sediments, in the guts of marine animals, and on the surface of decomposing fish. Inside of the marine organisms, it can act as a parasite.

References

http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=659

http://www.microbiologyatlas.kvl.dk/biologi/english/showmorf.asp?articleid=44

http://www.disknet.com/indiana_biolab/b203.htm

http://www.biology.pl/bakterie_sw/index_en.html

http://cibt.bio.cornell.edu/programs/archive/0608alum/lumos.pdf

http://web.mst.edu/~microbio/BIO221_2005/P_phosphoreum.htm