Steroidobacter flavus sp. nov., a microcystin-degrading Gammaproteobacterium isolated from soil

A microcystin-degrading strain, designated CPCC 100154 T , was isolated from a forest soil sample collected from Hainan Island, South China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CPCC 100154 T is affiliated to the family Sinobacteraceae in Gammaproteobacteria, with high 16S rRNA gene sequence similarities of 98.1, 96.6 and 96.6 % to Steroidobacter agariperforans JCM 18477 T , S. denitrificansis DSM 18526 T , and Povalibacter uvarum JCM 18749 T , respectively. In the phylogenetic tree based on 16S rRNA gene sequences, strain CPCC 100154 T formed a stable phylogenetic subclade with S. agariperforans JCM 18477 T , which indicated that strain CPCC 100154 T should be identified as a member of the genus Steroidobacter. The phylogenetic analysis based on partial gyrB gene sequences confirmed the affiliation of strain CPCC 100154 T to the genus Steroidobacter. While the DNA–DNA hybridization value (47.0 ± 1.7 %) between the new isolate and its near phylogenetic neighbor S. agariperforans JCM 18477 T was far below 70 %, which demonstrated that strain CPCC 100154 T represents a different genomic species from S. agariperforans. The strain CPCC 100154 T was found to be a Gram-stain negative, rod-shaped, motile with a polar flagellum, non-endospore-forming bacterium. Good growth was observed at 28–32 °C and pH 7.0–7.5. Polar lipids were identified to be diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, a unidentified phospholipid, an aminophospholipid and an unidentified aminolipid. The polyamine pattern was determined to contain spermidine as the predominant polyamine, moderate amounts of putrescine as well as traces of sym-homospermidine and spermine. The respiratory quinone was identified as ubiquinone-8. The major cellular fatty acids were found to include summed feature 3 (C 16: 1 ω7C/C 16: 1 ω6C) (46.1 %) and C 16: 0 (29.6 %). The genomic DNA G+C content was determined to be 64.4 mol%. On the basis of the above polyphasic taxonomy evidence, a novel species, Steroidobacter flavus sp. nov. is proposed. The type strain is CPCC 100154 T (=DSM 23339 T =CGMCC 1.10759 T ).