Description and Genome-Based Analysis of Vibrio chaetopteri sp. nov., a New Species of the Mediterranei Clade Isolated from a Marine Polychaete

Two novel strains, CB1-14^T and CB2-10, were isolated from the marine polychaetes <i>Chaetopterus cautus</i> from the Sea of Japan. Phylogenetic analysis based on the 16S rRNA sequences revealed that the two strains belong to the genus <i>Vibrio</i>, sharing 98.96% identity with <i>Vibrio hangzhouensis</i> CN 83^T. MLSA using five protein-coding genes (<i>ftsZ, gyrA, gyrB, mreB</i>, and <i>rpoA</i>) showed that CB1-14^T and CB2-10 are closely related to the members of the Mediterranei clade, namely <i>Vibrio mediterranei</i> CECT 621^T, <i>Vibrio barjaei</i> 3062^T, <i>Vibrio thalassae</i> CECT 8203^T, <i>Vibrio hangzhouensis</i> CGMCC 1.7062^T, <i>Vibrio maritimus</i> CAIM 1455^T, and <i>Vibrio variabilis</i> CAIM 1454^T. Based on both MLST neighbor-net phylogenetic network and phylogenomic tree results, they fell into the subclade formed by <i>V. maritimus</i> CAIM 1455^T and <i>V. variabilis</i> CAIM 1454^T. Both new strains CB1-14^T and CB2-10 showed the highest ANI/AAI values of 91.3%/92.7% with <i>V. variabilis</i> CAIM 1454^T and 90.3%/93.1% with <i>V. maritimus</i> CAIM 1455^T. The dDDH values between strain CB1-14^T and the members of the Mediterranei clade ranged from 20.9% to 45.7%. Major fatty acids were C_16:1<i>ω</i>9<i>c</i>, C_16:1<i>ω</i>7<i>c</i>, and C_18:1<i>ω</i>9<i>c</i>, followed by C_16:0 and C_18:1<i>ω</i>7<i>c</i>. The genome of CB1-14^T is 5,591,686 bp in size, with DNA G+C content of 46.1%. It consists of two circular chromosomes (3,497,892 and 1,804,652 bp) and one plasmid (241,015 bp) and comprises 4782 protein-coding genes and 10 <i>rrn</i> operons. The CB1-14^T and CB2-10 genomes were enriched in CAZyme-encoding genes of the following families: GH1, GH3, GH13, GH23, GH43, GH94, PL17, and CE4, indicating the potential to catabolize alginate, xylan, and chitin, common polysaccharides in marine ecosystems. Based on the combined phylogenomic analyses and phenotypic properties, a new species, <i>Vibrio chaetopteri</i> sp. nov., is proposed, with CB1-14^T = (KMM 8419^T = KCTC 92790^T) as the type strain.