Kaistina daejeonensis gen. nov., sp. nov. and Kaistina koreensis sp. nov., a novel nitrogen-fixing genus in the order Rhizobiales in α-2 subclass of the Proteobacteria

Abstract

Two Gram-negative, non-motile, non-spore-forming rods (strains $Y5^T$ and $Y9^T$) were isolated from contaminated phototrophic bacterial strains of the species Rhodopseudomonas palustris, and were investigated using a polyphasic taxonomic approach. Phylogenetic analysis based on the16S rRNA gene sequences showed that strains $Y5^T$ and $Y9^T$ are most closely related to the cluster comprising species in the Rhizobiales in the α-subclass of the Proteobacteria. Comparison of phylogenetic data indicated that they were most closely related to Methylocystis echinoides (91.7% & 91.4% similarity in 16S rDNA sequence). Ubiquinone Q-10 was detected in both strains and no menaquinone was detected. Strains $Y5^T$ and $Y9^T$ have cellular fatty acid profiles containing major amounts of saturated, unsaturated and cyclo fatty acids; the major fatty acids are $C_{18:1}$, $C_{16:0}$, $C_{18:0}$ and $C_{19:0}$ cyclo ω8c. The G + C contents of genomic DNA of strains $Y5^T$ and $Y9^T$ were 64.2% and 65.1%. The 16S rRNA gene sequence similarity between strains $Y5^T$ and $Y9^T$ is 98.5% and the mean level of DNA-DNA relatedness between the two strains is 51.4%. On the basis of phenotypic and phylogenetic data and genomic distinctiveness, it is proposed that strains $Y5^T$ and $Y9^T$ should be placed in a new genus, Kaistina gen. nov., as two distinct new species, for which the names Kaistina daejeonensis sp. nov. and Kaistina koreensis sp. nov. are proposed. The type strains are $Y5^T (= KCTC 12245^T =)$ and $Y9^T (= KCTC 12246^T)$, respectively.