A strictly aerobic bacteriochlorophyll a-containing alphaproteobacterium, designated strain S08T, was isolated from a biofilm sampled at Tama River in Japan. The non-motile and rod-shaped cells formed pink-beige pigmented colonies on agar plates containing organic compounds and showed in vivo absorption maxima at 798 and 866 nm in the near-infrared region, typical for the presence of bacteriochlorophyll a. The new bacterial isolate is Gram-negative, oxidase-negative and catalase-positive. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain S08T was closely related to species in the genus Roseomonas. The closest phylogenetic relative of strain S08T was Roseomonas lacus TH-G33T (98.2 % sequence similarity). The major cellular fatty acids were C16 : 0, C18 : 1 2-OH and summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c). The predominant respiratory quinone was ubiquinone-9. The major polar lipids contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an aminolipid. The G+C content of the genomic DNA was 70.6 mol%. The average nucleotide identity and digital DNA-DNA hybridization values between strain S08T and the related Roseomonas type strains were all far lower than the cut-off value for the delineation of species. The results of polyphasic comparisons showed that strain S08T was clearly distinguishable from other members of the genus Roseomonas. Therefore, we propose a new species in the genus Roseomonas, namely, Roseomonas fluvialis sp. nov. The type strain is S08T (=DSM 111902T=NBRC 112025T).
Keywords: AAPB; Aerobic anoxygenic phototrophic bacteria; BChl; bacteriochlorophyll; epilithic biofilm; river.