Members of candidate phylum OP9 are found in geothermal systems, petroleum reservoirs, anaerobic digesters, wastewater treatment facilities, and marine sediments. In this study, 8 single-cell genomes (SCGs) of OP9, which was predominant composing 26.7% in the marine sediments of the Ross Sea, Antarctica was obtained through single-cell sequencing. Eight SCGs showed high 16S rRNA gene identity (>99.3%) each other while they had low 16S rRNA gene similarities ( -Yet, little information regarding their metabolic capabilities and ecological role within such habitats is currently available due to the lack of cultured isolates. -As a first study on the OP9 genome from Antarctic marine sediment, more detailed analyses will provide the glimpse into the lifestyle of a member of widely distributed, yet poorly understood bacterial candidate division OP9.