We isolated an obligately anaerobic halophilic bacterium from the Dead Sea that grew by respiration of selenate. The isolate, designated strain DSSe-1, was a gram-negative, non-motile rod. It oxidized glycerol or glucose to acetate+CO2 with concomitant reduction of selenate to selenite plus elemental selenium. Other electron acceptors that supported anaerobic growth on glycerol were nitrate and trimethylamine-N-oxide; nitrite, arsenate, fumarate, dimethylsulfoxide, thiosulfate, elemental sulfur, sulfite or sulfate could not serve as electron acceptors. Growth on glycerol in the presence of nitrate occurred over a salinity range from 100 to 240 g/l, with an optimum at 210 g/l. Analysis of the 16S rRNA gene sequence suggests that strain DSSe-1 belongs to the order Halanaerobiales, an order of halophilic anaerobes with a fermentative or homoacetogenic metabolism, in which anaerobic respiratory metabolism has never been documented. The highest 16S rRNA sequence similarity (90%) was found with Acetohalobium arabaticum (X89077). On the basis of physiological properties as well as the relatively low homology of 16S rRNA from strain DSSe-1 with known genera, classification in a new genus within the order Halanaerobiales, family Halobacteroidaceae is warranted. We propose the name Selenihalanaerobacter shriftii. Type strain is strain DSSe-1 (ATCC accession number BAA-73).
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Acknowledgements We thank Skipper Moti Gonen and his crew for their help with sample collection during the Dead Sea cruise, and A. Burns Bindi and S.E. Hoeft for technical assistance. We are grateful to M. Herbel for advice on the quantification of Se0, and to D. Newman and B.F. Taylor for their comments on the original manuscript. This study was funded in part by a grant from the Israeli Ministry of National Infrastructures (to A.O.), by the U.S. Geological Survey, and by EPA R826105 (to J.S.).
- Dead Sea
- Nitrate reduction
- Selenate reduction
- Selenihalanaerobacter shriftii gen. nov. sp. nov.