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 Chaetopterus cautus from the Sea of Japan. Phylogenetic analysis based on the 16S rRNA sequences revealed that the two strains belong to the genus Vibrio, sharing 98.96% identity with Vibrio hangzhouensis CN 83(T). MLSA using five protein-coding genes (ftsZ, gyrA, gyrB, mreB, and rpoA) showed that CB1-14(T) and CB2-10 are closely related to the members of the Mediterranei clade, namely Vibrio mediterranei CECT 621(T), Vibrio barjaei 3062(T), Vibrio thalassae CECT 8203(T), Vibrio hangzhouensis CGMCC 1.7062(T), Vibrio maritimus CAIM 1455(T), and Vibrio variabilis CAIM 1454(T). Based on both MLST neighbor-net phylogenetic network and phylogenomic tree results, they fell into the subclade formed by V. maritimus CAIM 1455(T) and V. variabilis CAIM 1454(T). Both new strains CB1-14(T) and CB2-10 showed the highest ANI/AAI values of 91.3%/92.7% with V. variabilis CAIM 1454(T) and 90.3%/93.1% with V. maritimus 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)ω9c, C(16:1)ω7c, and C(18:1)ω9c, followed by C(16:0) and C(18:1)ω7c. 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 rrn 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, Vibrio chaetopteri sp. nov., is proposed, with CB1-14(T) = (KMM 8419(T) = KCTC 92790(T)) as the type strain.