No abstract

ABSTRACT

Two isolates, designated CadH11T and Cad448T, representing uncultured purple sulfur bacterial populations H and 448, respectively, in the chemocline of Lake Cadagno, a crenogenic meromictic lake in Switzerland, were obtained using enrichment and isolation conditions that resembled those used for cultured members of the genus Thiocystis. Phenotypic, genotypic and phylogenetic analyses of these isolates confirmed their assignment to the genus Thiocystis. However, 16S rRNA gene sequence similarities of 98.2 % between CadH11T and Cad448T, and similarities of 97.7 and 98.5 %, respectively, with their closest cultured relative Thiocystis gelatinosa DSM 215T, as well as differences in DNA G+C content and carbon source utilization suggested that the isolates belonged to two distinct species. DNA–DNA hybridization of CadH11T and Cad448T with T. gelatinosa DSM 215T showed relatedness values of 46.4 and 60.8 %, respectively; the relatedness value between CadH11T and Cad448T was 59.2 %. Based on this evidence, strains CadH11T and Cad448T represent two novel species within the genus Thiocystis, for which the names Thiocystis chemoclinalis sp. nov. and Thiocystis cadagnonensis sp. nov. are proposed, respectively. The type strains of T. chemoclinalis sp. nov. and T. cadagnonensis sp. nov. are CadH11T ( = JCM 15112T  = KCTC 5954T) and Cad448T ( = JCM 15111T  = KCTC 15001T), respectively.