Desulfovibrio salexigens DSM 2638 (Desulfovibrio salexigens British Guiana NCIMB 8403) is an anaerobic, marine sulfate reducer that has an absolute requirement of more than 0.5% (wt/vol) NaCl for growth. It was isolated from “sling mud”* from British Guiana about 1951 or 52. It is described as a “fat vibrio” with a single, polar flagellum that grows at 30ºC (1). The GC % is rather different from other Desulfovibrio species so far sequenced, being reported to be 49%. It has also been listed among those sulfate reducers capable of nitrogen fixation, possibly linked to the phosphoroclastic reaction (2). D. salexigens appears to show a 40 to 400 fold increased resistance to the inhibitor hibitane versus D. vulgaris and Gram+ sulfate reducers (3). In non-optimal growing conditions, D. salexigens is pleiomorphic in that it forms coccoid structures. Of most interest, is the salt requirement and tolerance of D. salexigens. As background, fresh-water strains (e.g., D. vulgaris) are generally inhibited by about 1% NaCl and none grows with more than 3% salt. Those from marine habitats or those that are tolerant (e.g., Desulfovibrio G20) may not require salt but grow up to about 7% NaCl. D. salexigens represents a type called “exigent” that has an absolute requirement for >0.5% NaCl and can grow at concentrations >10%. The requirement has been demonstrated by ion replacement tests to be for chloride not sodium! Sequencing of the genome of this bacterium may provide directions to explore the differences in the adaptations to life in extreme saline conditions. References 1. Postgate, J.R. 1984 The Sulphate-Reducing Bacteria (2nd ed.) Cambridge University Press, Cambridge, London. |
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Desulfovibrio salexigens DSM 2638
