한국인 구강에서 분리된 Capnocytophaga ochracea와 Selenomonas sputigena의 동정 및 특성화

Abstract

Background and objectives: Three strains (KCOM 2191, KCOM 2668, and KCOM 2812) of Capnocytophaga ochracea and two strains (KCOM 1787 and KCOM 2046) of Selenomonas sputigena were isolated from a Korean population and deposited to the Korean Collection for Oral Microbiology. These strains were classified at the species level by comparing their 16S ribosomal RNA gene (16S rDNA) sequences. Considering that the gold standards for bacterial classification at the species level are 16S rDNA sequencing and digitalized DNA-DNA hybridization, average nucleotide identity (ANI) and genome-to-genome distance (GGD) analysis, based on whole genome sequence (WGS), it is not enough to classify them as C. ochracea or S. sputigena at the species-level. Therefore, the purpose of this study was to classify these strains at the species-level based on WGS and additionally investigate their morphological, biochemical, and chemotaxonomical characteristics. Methods: WGSs of five strains were determined using PacBio RSII and/or Illumina platform. ANI and GGD analysis were used to classify them at the species-level. Cellular fatty acid (CFA) compositions of the five strains were determined using MIDI/Hewlett Packard Microbial Identification System. Their polar lipids were analyzed using thin-layer chromatography. Their quinones were determined using high-performance liquid chromatography. Results: As a result of determining WGSs of the five strains, all were determined as one contig. As a result of ANI analysis, KCOM 2191, KCOM 2668, and KCOM 2812 strains had ANI values above 96.3% with C. ochracea DSM 7271T, and KCOM 1787 and KCOM 2046 strains showed ANI values above 95.3% with S. sputigena ATCC 35185T. As a result of analysis of CFAs, KCOM 2191, KCOM 2668, and KCOM 2812 strains had the highest amount of iso-C15:0 at 57.9%, 67.2%, and 64.9%, respectively. This result was similar to that of the C. ochracea DSM 7271T (51.5%). Major CFAs of KCOM 1787 and KCOM 2046 were C14:0 DMA, C16:1 cis-7, C18:1 at 17.254, C17:1 cis-9/C17:2, and C15:2/UN 14.762 C15:2, which accounted for approximately 10 %. Major CFAs of S. sputigena ATCC 35185T were C14:0 DMA (35.6%), C15:0 (11.1%), and C11:0 (10.9%), different from the two strains used in this study. As a result of morphological characteristics, biochemical tests, and quinone analysis, it was found that the five strains used in this study had characteristics similar to those of each type strain. Conclusion: Results indicate that KCOM 2191, KCOM 2668, and KCOM 2812 strains belong to C. ochracea, and KCOM 1787 and KCOM 2046 strains belong to S. sputigena. These strains could be used to study the pathogenesis of oral as well as systemic diseases dependent on C. ochracea and S. sputigena.