Three aerobic, Gram-stain-negative, non-motile, rod-shaped bacteria, designated as strains SHINM1T, ICHIJ1 and ICHIAU1, were isolated from surface river water (Saitama Prefecture, Japan). Phylogenetic analyses based on 16S rRNA and 40 marker gene sequences revealed that the strains formed a distinct phylogenetic lineage within the order Rhodocyclales. The three strains shared 100 % 16S rRNA gene similarity. Growth occurred at 15-30 °C and pH 6.0-9.5, but not in the presence of ≥1.0 % (w/v) NaCl. The isolates stained positive for intracellular polyphosphate granules. The major cellular fatty acids were C16 : 0, summed feature 2 (C12 : 1 aldehyde and/or iso-C16 : 1 I and/or C14 : 0 3-OH), summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The major polar lipids were phosphatidylethanolamine and an unidentified phospholipid. The predominant quinone system of strain SHINM1T was ubiquinone-8 and its DNA G+C content was 56.7 mol%. Genome sequencing of the three isolates revealed a genome size of 2.29-2.43 Mbp and average nucleotide identity by orthology values of ≥98.9 %. Based on the results of phenotypic and phylogenetic analyses, strains SHINM1T, ICHIJ1 and ICHIAU1 represent a novel species of a new genus, for which the name Fluviibacter phosphoraccumulans gen. nov., sp. nov. is proposed, within a new family, Fluviibacteraceae fam. nov. of the order Rhodocyclales. The type strain is SHINM1T (=JCM 32071T=NCIMB 15105T).
Keywords: Rhodocyclaceae; bacterioplankton; polyphosphate accumulation; surface river water.