Diaphorobacter oryzae sp. nov., isolated from a thiosulfate-oxidizing enrichment culture.

A taxonomic study was performed on two isolates, strains RF3T and RF21, recovered from a thiosulfate-oxidizing enrichment culture. Comparative 16S rRNA gene sequence analysis showed that these isolates were clearly affiliated with the class Betaproteobacteria. Strains RF3T and RF21 were most closely related to Diaphorobacter nitroreducens NA10BT (97.9 and 98.2 % 16S rRNA gene sequence similarity, respectively). The level of 16S rRNA gene sequence similarity between strains RF3T and RF21 was 99.8 %. The two isolates were Gram-negative, aerobic and denitrifying. Growth was observed at 7–35 °C. Physiological and biochemical properties of strains RF3T and RF21 were different from those of D. nitroreducens NA10BT in that strains RF3T and RF21 were able to utilize l-histidine, 2-ketogluconate and caprate, but unable to utilize suberate. The G+C contents of the genomic DNA of strains RF3T and RF21 were 62.9 and 62.8 mol%, respectively, and the predominant quinone was ubiquinone-8. Strains RF3T and RF21 possessed C16 : 0, C17 : 0 cyclo, and C16 : 1 ω7c and/or iso-C15 : 0 2-OH as major fatty acids. DNA–DNA relatedness data indicated that strains RF3T and RF21 represent a genomic species separate from D. nitroreducens. On the basis of the evidence presented from this polyphasic analysis, it is suggested that strains RF3T and RF21 represent a novel species of the genus Diaphorobacter, for which the name Diaphorobacter oryzae sp. nov. is proposed. The type strain is RF3T (=KCTC 22225T=LMG 24467T).