Roseobacter cerasinus sp. nov., isolated from a fish farm

An obligate aerobic and bacteriochlorophyll a-containing bacterium, designated strain AI77^T, was isolated from a fish farm in Uwa Sea, Japan. Cells were Gram-stain-negative, coccoid- to oval-shaped, and showed no motility. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain AI77^T is a member of the genus Roseobacter and closely related to Roseobacter ponti MM-7^T (97.8 %), Roseobacter denitrificans OCh 114^T (97.3 %) and Roseobacter litoralis OCh 149^T (97.3 %). The G+C content of strain AI77^T was 61.0 mol%. The average amino acid identity values of the genome in strain AI77^T with those in R. denitrificans OCh 114^T and R. litoralis OCh 149^T were 73.26 % (SD 16.46) and 72.63 % (SD 16.76), respectively. The digital DNA-DNA hybridization values of strain AI77^T with the type strains R. denitrificans OCh 114^T and R. litoralis OCh 149^T were 18.70 and 18.50 %, respectively. The dominant fatty acids (>10 % of total fatty acids) of AI77^T were summed feature 8 (C_18 : 1 ω7c and/or C_18 : 1 ω6c) and saturated fatty acid C_16 : 0. The sole respiratory quinone was ubiquinone-10. The predominant polar lipids were phosphatidylcholine, phosphatidylglycerol and diphosphatidylglycerol. Based on the genetic and phenotypic data obtained herein, we conclude that strain AI77^T represents a new species of the genus Roseobacter, for which we propose the name Roseobacter cerasinus sp. nov.; the type strain is AI77^T (=DSM 110091^T=NBRC 114115^T).