Photobacterium profundum
| Photobacterium profundum | |
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| Confocal image of P. profundum Strain SS9 expressing a green fluorescent protein. Bar: 10μm | |
| Scientific classification | |
| Kingdom: | Bacteria |
| Phylum: | Proteobacteria |
| Class: | Gammaproteobacteria |
| Order: | Vibrionales |
| Family: | Vibrionaceae |
| Genus: | Photobacterium |
| Species: | P. profundum |
| Binomial name | |
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Photobacterium profundum |
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Photobacterium profundum is a deep sea Gammaproteobacterium, belonging to the family Vibrionaceae and genus Photobacterium. Like other members of this genus, P. profundum is a marine organism and has two circular chromosomes.P. profundum is a gram-negative rod with the ability for growth at temperatures from 0 °C to 25 °C and pressures from 0.1 MPa to 70 MPa depending on the strain. It has a requirement for salt, is able to metabolise a wide range of simple and complex carbohydrates and has two flagella systems. Cells are rod shape, 2-4μm long and 0.8-1.0μm wide, with a single unsheathed flagella. This bacterium was originally isolated in 1986 from the Sulu Sea and there are currently 4 cultured wild-type strains of P. profundum, (strains SS9, 3TCK, DJS4 and 1230).
P. profundum strain SS9 has optimal growth at 15 °C and 28 MPa making it both a psychrophile and a piezophile. P. profundum strain 3TCK, isolates from San Diego Bay, grows optimally at 9 °C and 0.1 MPa and P. profundum strain DSJ4, isolated from the Ryukyu Trench off of Japan at a depth of 5110 m, grows optimally at 10 °C and 10 MPa. Based on 16S rRNA sequence P. profundum is closely related to the Vibrio genus, the most prominent species being the human pathogen Vibrio cholerae.
In strain SS9 it has been shown that several stress response genes are up regulated in response to atmospheric pressure, these include htpG, dnaK, dnaJ, and groEL. The types and abundance of fatty acid chains in the cell membrane also respond to changes in pressure and temperature. At low temperature and high pressure strain SS9 increases the abundance of mono- and polyunsaturated fatty acids. This has the effect of increasing membrane fluidity by reducing packing of the fatty acid chains which results in a liquid crystal structure in the membrane rather than a gel structure. The outer membrane protein OmpH has been shown to be up regulated at elevated pressures, the opposite is true for the outer membrane protein OmpL which is up regulated in response to low pressures.
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