A yellow-coloured, Gram-strain-negative, non-motile, cocci-shaped, strictly aerobic bacterium, designated HZ-65T, was isolated from hyporheic freshwater in the Republic of Korea. Strain HZ-65T grew at 15-37 °C (optimum, 25-30 °C), pH 5.5-9.0 (optimum, pH 7.0) and 0-0.5 % NaCl (w/v; optimum at 0 % NaCl). Phylogenetic analysis based on the 16S rRNA gene showed that strain HZ-65T is a member of family Opitutaceae and is closely related to Opitutus terrae PB90-1T (94.0 % similarity), Cephaloticoccus primus CAG34T (93.0 %), and Cephaloticoccus capnophilus CV41T (92.7 %), while the similarities to other Opitutaceae-type strains were lower than 90.0 %. The DNA G+C content was 62.2 mol% and the quinone present was menaquinone-7. The predominant fatty acids were iso-C14 : 0, anteiso-C15 : 0, C16 : 0, and iso-C16 : 0, representing 70 % of the total fatty acids. The major polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. Analysis of the HZ-65T genome revealed the presence of 300 genes that are involved in carbohydrate-active enzymes, which indicates the metabolic potential to degrade polysaccharides. The phenotypic, chemotaxonomic, genetic, and phylogenetic properties suggest that strain HZ-65T represents a novel species in a new genus within the family Opitutaceae, for which the name Nibricoccus aquaticus gen. nov., sp. nov., is proposed. The type strain of Nibricoccus aquaticus is HZ-65T (KACC 19333T=NBRC 112907T).
Keywords: Nibricoccus; Nibricoccus aquaticus; class Opitutae; hyporheic freshwater; phylum Verrucomicrobia; polyphasic taxonomy.