A strictly aerobic, bacteriochlorophyll (BChl) a-containing alphaproteobacterium, designated strain K6T, was isolated from seawater around an aquaculture site in the Uwa Sea in Japan. The novel strain grew optimally at 30 °C at pH 7.0-7.5 and in the presence of 2.0 % (w/v) NaCl. The nonmotile and coccoid or rod-shaped cells formed pink-pigmented colonies on agar plates containing organic compounds. Cells showed an in vivo absorption maximum at 870 nm in the near-infrared region, indicating the presence of BChl a in the light-harvesting 1 complex. The new bacterial strain was Gram-stain-negative and oxidase- and catalase-positive. Phylogenetic analysis based on the 16S rRNA gene sequence showed that strain K6T was closely related to species in the genus Litoreibacter. The closest phylogenetic relatives of strain K6T were Litoreibacter ponti GJSW-31T (98.56 % sequence similarity), Litoreibacter janthinus KMM 3842T (97.63 %) and Litoreibacter albidus KMM 3851T (96.88 %). The G+C content of the genomic DNA was 58.26 mol%. The average nucleotide identity value of strain K6T with the type strain of L. ponti was 77.16 % (SD 4.79 %). The digital DNA-DNA hybridization value of strain K6T with the type strain of L. ponti was 19.40 %. The respiratory quinone was ubiquinone-10. The major cellular fatty acids were C18 : 1 ω7c, C16 : 0 and 11-methyl C18 : 1 ω7c. The dominant polar lipids were phosphatidylcholine and phosphatidylglycerol. On the basis of the genetic and phenotypic data obtained in the present study, we propose a new species in the genus Litoreibacter: Litoreibacter roseus sp. nov., whose type strain is K6T (=DSM 110109T=NBRC 114114T). Strain K6T represents the first confirmed species that produces BChl a within the genus Litoreibacter.
Keywords: Litoreibacter; aerobic anoxygenic phototrophic bacteria; aquaculture; bacteriochlorophyll a.