Roseicitreum antarcticum gen. nov., sp. nov., an aerobic bacteriochlorophyll a-containing alphaproteobacterium isolated from Antarctic sandy intertidal sediment.

A novel Gram-negative, non-motile bacterium, designated strain ZS2-28(T), was isolated from sandy intertidal sediment samples collected from the coastal regions of the Chinese Antarctic Zhongshan Station on the Larsemann Hills, Princess Elizabeth Land, East Antarctica. Strain ZS2-28(T) was obligately heterotrophic, strictly aerobic, psychrotolerant (growth occurred at 0-33 °C) and moderately halophilic (optimal growth in 7-8 % NaCl). A single major peak at 872-874 nm in the infrared absorption spectrum indicated the presence of bacteriochlorophyll a. Poly-β-hydroxybutyrate accumulation and slime production were also detected. The predominant cellular fatty acid was C₁₈:₁ω7c, with C₁₀:₀ 3-OH, C₁₆:₀, C₁₇:₀ cyclo, C₁₉:₀ω8c cyclo and summed feature 3 (C₁₆:₁ω7c and/or iso-C₁₅:₀ 2-OH) present in smaller amounts. The respiratory quinone was Q-10. The main polar lipids were phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an unidentified aminolipid. The G+C content of the genomic DNA was 63.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain ZS2-28(T) formed a distinct evolutionary lineage within the clade containing members of the genera Roseibaca, Roseinatronobacter and Rhodobaca of the class Alphaproteobacteria. On the basis of its phylogenetic position, as well as its phenotypic and chemotaxonomic characteristics, strain ZS2-28(T) represents a novel species of a novel genus, for which the name Roseicitreum antarcticum gen. nov., sp. nov. is proposed. The type strain is ZS2-28(T) ( = CGMCC 1.8894(T)  = LMG 24863(T)).