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

Two novel strains, CB1-14 and CB2-10, were isolated from the marine polychaetes from the Sea of Japan. Phylogenetic analysis based on the 16S rRNA sequences revealed that the two strains belong to the genus , sharing 98.96% identity with CN 83. MLSA using five protein-coding genes (, and ) showed that CB1-14 and CB2-10 are closely related to the members of the Mediterranei clade, namely CECT 621, 3062, CECT 8203, CGMCC 1.7062, CAIM 1455, and CAIM 1454. Based on both MLST neighbor-net phylogenetic network and phylogenomic tree results, they fell into the subclade formed by CAIM 1455 and CAIM 1454. Both new strains CB1-14 and CB2-10 showed the highest ANI/AAI values of 91.3%/92.7% with CAIM 1454 and 90.3%/93.1% with CAIM 1455. The dDDH values between strain CB1-14 and the members of the Mediterranei clade ranged from 20.9% to 45.7%. Major fatty acids were C9, C7, and C9, followed by C and C7. The genome of CB1-14 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 operons. The CB1-14 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, sp. nov., is proposed, with CB1-14 = (KMM 8419 = KCTC 92790) as the type strain.