Rhizorhabdus phycosphaerae sp. nov., isolated from the phycosphere of Microcystis aeruginosa

Abstract

A novel bacterial strain, designated MK52(T), was isolated from the phycosphere of Microcystis aeruginosa . Strain MK52(T) is a Gram-stain-negative, pink-pigmented, rod-shaped, strictly aerobic bacterium. In 16S rRNA phylogenetic analysis, the MK52(T) strain was most closely related to Rhizorhabdus wittichii RW1(T) (98.66 %) and Rhizorhabdus histidinilytica UM2(T) (98.51 %). The genomic DNA G+C content of strain MK52(T) was calculated to be 65.5 mol%. The average nucleotide identity values of strain MK52(T) with R. wittichii RW1(T) and R. histidinilytica UM2(T) were 80.35 and 80.23 %, respectively, with digital DNA-DNA hybridization values of 23.6 and 22.9 %, respectively, and average amino acid identities of 75.59 and 75.79 %, respectively. The major isoprenoid quinone was Q-10, and the predominant polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and sphingoglycolipid. Fatty acid methyl ether analysis showed that summed feature 8 (C-18 : 1 omega 7c and/or C-18 : 1 omega 6c) was the main cellular fatty acid in strain MK52(T). Strain MK52(T) cells grew at 21-34 degrees C (optimum, 30 degrees C), pH 5-8 (optimum, pH 7) and with 0-2 % (w/v) NaCl (optimum, 0.5 % NaCl). Rhizorhabdus phycosphaerae sp. nov. is proposed as a new species (=KCTC 72877(T)=DSM 111424(T)) based on its genotypic and phenotypic characteristics.