Thioalkalivibrio thiocyanoxidans sp nov and Thioalkalivibrio paradoxus sp nov., novel alkaliphilic, obligately autotrophic, sulfur-oxidizing bacteria capable of growth on thiocyanate, from soda lakes

Nine strains of haloalkaliphilic, obligately autotrophic, sulfur-oxidizing bacteria able to grow with thiocyanate (SCN-) as the sole energy and nitrogen source were isolated from soda lakes in South-East Siberia, Kenya and Egypt after enrichment on sodium carbonate minerals buffered at pH 10 with thiocyanate as the substrate. The isolates fell into two groups that were substantially different in terms of cell morphology, growth parameters and the ability to oxidize carbon disulfide. The bacteria were able to oxidize sulfide, polysulfide, sulfur and tetrathionate, as well as thiocyanate. Two isolates belonged to an extremely halotolerant type growing in the presence of up to 4 M Na+. Cyanate (CNO-) was the main nitrogen-containing intermediate during thiocyanate degradation in both groups. According to DNA-DNA hybridization data and phylogenetic analysis, both groups of isolates belong to a recently described genus of haloalkaliphillic sulfur-oxidizing bacteria, i.e. Thioalkalivibrio, belonging to the gamma-Proteobacteria, in which where they represent two new species. The species name Thioalkalivibrio paradoxus (type strain ARh 1(T) = DSM 13531(T) = JCM 11367(T)) is proposed for the group with barrel-shaped cells, and the species name Thioalkalivibrio thiocyanoxidans (type strain ARh 2(T), DSM 13532(T) = JCM 11368(T)) is proposed for the group with vibrio-shaped cells. The diagnosis of the genus Thioalkalivibrio is amended according to the new data.