Selenihalanaerobacter shriftii gen. nov., sp nov., a halophilic anaerobe from Dead Sea sediments that respires selenate

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 gramnegative, non-motile rod. It oxidized glycerol or glucose to ac etate+CO2 with concomitant reduction of selenate to selenite plus elemental selenium. Other electron accepters that supported anaerobic growth on glyc erol were nitrate and trimethylamine-N-oxide; nitrite, arsenate, fumarate, dimethylsulfoxide, thiosulfate. elemental sulfur, sulfite or sulfate could not serve as electron accepters. Growth on glycerol in the presence of nitr ate 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 wit h a fermentative or homoacetogenic metabolism, in which anaerobic respirato ry metabolism has never been documented. The highest 16S rRNA sequence simi larity (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 wi thin the order Halanaerobiales, family Halobacteroidaceae is warranted. We propose the name Selenihalanaerobacter shriftii. Type strain is strain DSSe -1 (ATCC accession number BAA-73).