Abstract
Two strains of haloalkaliphilic, obligately autotrophic, sulfur-oxidizing bacteria were isolated from the oxygen-sulfide interface water layer of stratified alkaline and saline Mono Lake, California, USA. Strain ALM 1(T) was a dominant species in enrichment on moderate-saline, carbonate-buffered medium (0.6 M total Na(+), pH 10) with thiosulfate as an energy source and nitrate as a nitrogen source. Cells of ALM 1(T) are open ring-shaped and are non-motile. It has a high growth rate and activity of thiosulfate and sulfide oxidation and very low sulfur-oxidizing activity. Genetic comparison and phylogenetic analysis suggested that ALM 1(T) (=DSM 14477(T)=JCM 11371(T)) represents a new species of the genus Thioalkalimicrobium in the gamma-Proteobacteria, for which the name Thioalkalimicrobium cyclicum sp. nov. is proposed. Another Mono Lake isolate, strain ALM 2(T), dominated in enrichment on a medium containing 2 M total Na(+) (pH 10). It is a motile vibrio which tolerates up to 4 M Na(+) and produces a membrane-bound yellow pigment. Phylogenetic analysis placed ALM 2(T) as a member of genus Thioalkalivibrio in the gamma-Proteobacteria, although its DNA hybridization with the representative strains of this genus was only about 30%. On the basis of genetic and phenotypic properties, strain ALM 2(T) (=DSM 14478(T)=JCM 11372(T)) is proposed as Thioalkalivibrio jannaschii sp. nov.