Natronospira proteinivora gen. nov., sp nov, an extremely salt-tolerant, alkaliphilic gammaproteobacterium from hypersaline soda lakes

Brine samples from Kulunda Steppe soda lakes (Altai, Russia) were inoculated into a hypersaline alkaline mineral medium with b-keratin (chicken feather) as a substrate. The micro-organisms dominating the enrichment culture were isolated by limiting serial dilution on the same medium with casein as a substrate. The cells of strain BSker1(T) were motile, curved rods. The strain was an obligately aerobic heterotroph utilizing proteins and peptides as growth substrates. The isolate was an obligate alkaliphile with a pH range for growth from pH 8.5 to 10.25 (optimum at pH 9.5), and it was extremely salt tolerant, growing with between 1 and 4.5 M total Na+ (optimally at 2-2.5 M). BSker1(T) had a unique composition of polar lipid fatty acids, dominated by two C-17 species. The membrane polar lipids included multiple unidentified phospholipids and two aminolipids. According to phylogenetic analysis of the 16S rRNA gene sequence, the isolate forms a novel branch within the family Ectothiorhodospiraceae (class Gammaproteobacteria) with the highest sequence similarity to the members of this family being 91 %. On the basis of distinct phenotypic and genotypic properties, strain BSker1T (=JCM 31341(T)=UNIQEM U1008(T)) is proposed to be classified as a representative of a novel genus and species, Natronospira proteinivora gen. nov., sp. nov.