Cultivation and genomic analyses of four marine flavobacterial strains affiliated with the NS5 marin

초록

Flavobacteriaceae is one of major bacterial groups in marine environments. While the family have been recognized to be rather readily culturable, many marine groups of the Flavobacteriaceae have no cultured representatives yet. Here we report on the isolation and genome sequences of the four flavobacterial strains belonging to the NS5 marine group, an abundant marine flavobacterial group with no cultured isolates. The four NS5 strains were isolated from coastal seawaters of the Korean Peninsula by dilution-to-extinction culturing. Analyses of 16S rRNA gene sequences showed that the four strains are phylogenetically novel with <92% similarities to other cultured bacteria. The genome sequences of the four strains were determined through PacBio and Illumina platform, and were annotated using IMG-ER pipeline. The sizes and G+C contents of the genomes were 2.11?2.50 Mbp and 35.9?40.0%, respectively. ANI values among the genomes were ~70%, indicating phylogenetic uniqueness of each strain within the NS5 group. All NS5 genomes showed general features of heterotrophic metabolisms. Like many other marine flavobacterial genomes, a large number of carbohydrate-active enzymes were predicted in the NS5 genomes. Gene pairs encoding SusCD proteins that denote polysaccharide utilization loci were also found in the genomes. The number of susCD gene pairs were ≥10 per each genome, except for one genome with only 2 pairs. Genes encoding light-harvesting rhodopsins were predicted in the all NS5 genomes. The four NS5 genomes would contribute to better understanding of genomic diversity of marine flavobacteria.