Inferred Metabolic Capabilities of Novel Marine Bacterial Clades of the Family Halieaceae

초록

The family Halieaceae (OM60/NOR5 clade) represents one of the most abundant bacterioplankton groups in the ocean surface. However, understanding of this lineage has been limited by insufficient cultured representatives and genomes. In this study, using the whole genomes of six strains belonging to family Halieaceae, which have been sporadically isolated from the Yellow Sea and the East Sea by dilution-to-extinction culturing or standard dilution plating, we conducted a comparative genomic analysis and metabolic reconstructions to investigate their evolution and ecology. The phylogenies indicated that these strains each represent a novel species assigned to five novel genera and genus Halioglobus. Three of the isolates were found to be the first cultured representatives of the uncultivated NOR5 subclades. Genome analysis revealed that all of them have heterotrophic lifestyles; five strains were featured by photoheterotrophy with harboring puf operons for aerobic anoxygenic phototrophy or greenabsorbing proteorhodopsin genes, coinciding with their adaptation to euphotic ocean surface. Carbohydrate utilization capability inferred from CAZyme analyses suggested that the strains might be closely associated with phytoplankton bloom. The cultures together with their genomes will provide a rich foundation for further study of the Halieaceae lineage using diverse approaches such as metatranscriptomics. [Supported by grant from the KIMST funded by the MOF, Korea (No. 20180430)]