Abstract

A Gram-negative aerobic bacterium, designated RR4-38T, was isolated from a biofilter in a seawater recirculating aquaculture system (RAS) in Busan, South Korea. The bacteria were irregular, short, rod-shaped, non-motile, oxidase-positive, and catalase-negative. Growth of the strain RR4-38T was observed at 15–35°C (optimum, 25–30°C), pH 5.5–9.5 (optimum, pH 8.0), and in the presence of 0–5% (w/v) NaCl (optimum, 3%). Phylogenetic analysis based on the 16S rRNA gene sequences showed that the strain RR4-38T formed a distinct lineage with close genera Ulvibacter (≤ 95.01% 16S rRNA gene sequence similarity), Aureitalea (94.74%), Aureisphaera (≤ 93.27%), and Jejudonia (93.07%) that all belong to the family Flavobacteriaceae. Whole-genome sequence comparison revealed that the ANI (average nucleotide identity) and digital DDH (DNA-DNA hybridization) values between strain RR4-38T and the two closest strains, Ulvibacter antarcticus DSM 23424T and Aureitalea marina S1-66T, were 68.96– 69.88% and 17.4–19%, respectively. The genome analysis revealed that the strain might be involved in biodegradation of organic debris produced by farmed fish in aquaculture systems. The predominant respiratory quinone was menaquinone MK-6 and the major cellular fatty acids were iso- C15:0 (26.5%), iso-C17:0 3-OH (16.4%), iso-C15:1 G (15%), and iso-C16:0 3-OH (9.6%). The major cellular polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, unidentified aminolipids, and glycolipids. Based on phenotypic, chemotaxonomic, and phylogenetic features, strain RR4-38T represents a novel genus and species in the family Flavobacteriaceae, for which the name Pukyongia salina gen. nov., sp. nov. is proposed. The type strain is RR4-38T (= KCTC 52651T = DSM 108068T).

• Keywords: COVID-19;SARS-CoV-2;coronavirus;natural compounds