Genome analysis of Rubritalea profundi SAORIC-165T isolated from deep seawater in the northwestern Pacific Ocean

초록

The phylum Verrucomicrobia has been found in diverse environments including soil, freshwater, marine environment, plant and human feces. Culture-independent studies have shown the presence of Verrucomicrobia in the deep sea, but deep-sea verrucomicrobial strains have been rarely cultured and characterized. Recently, Rubritalea profundi SAORIC-165T, a psychrophilic strain of the phylum Verrucomicrobia, was isolated from a depth of 2,000 m in the northwestern Pacific Ocean. Amplicon sequencing of 16S rRNA genes of the water column where the strain was isolated showed that the genus Rubritalea was abundant at the same depth (2,000 m), suggesting that the strain SAORIC-165T may represent a deep-sea verrucomicrobial population (Song et al., 2017). In this study, we analyzed the genome of Rubritalea profundi SAORIC-165T, the first deep-sea verrucomicrobial genome to our knowledge. The draft genome of strain SAORIC-165T was 4,167,407 bp in length, with a G+C content of 47.5 %. The SAORIC-165T genome contains genes for central carbon metabolic pathways, such as the Embden-Meyerhof pathway, the pentose phosphate pathway, the tricarboxylic acid (TCA) cycle, the glyoxylate cycle, and the Entner-Doudoroff pathway. Pathways for dissimilatory nitrate reduction, denitrification, and assimilatory/dissimilatory sulfate reduction were partially predicted. Comparison against other Rubritalea genomes from surface seawater revealed that the SAORIC-165T genome is enriched in genes involved in mobile elements, signal transduction, polysaccharide lysis, and adhesion, some of which were related to adaptation to deep-sea environment. These findings suggest that Rubritalea profundi SAORIC-165T represents a phylogenetically unique and ecologically relevant verrucomicrobial group in deep-sea environments.