Sphingomonas caeni sp. nov., a phenolic acid-degrading bacterium isolated from activated sludge.

A Gram-stain-negative, rod-shaped, polar flagellated or stalked and non-spore-forming bacterium, designated LB-2, was isolated from activated sludge. Growth was observed at 20-30 °C (optimum 28 °C), pH 6.0-8.0 (optimum pH 7.0) and salinity of 0-0.5% (w/v; optimum 0.5%). Phylogenetic analysis based on the 16S rRNA gene indicated that strain LB-2 belongs to the genus Sphingomonas and showed the highest sequence similarity (96.7%) and less than 96.7% similarities to other type strains. The genome size of strain LB-2 was 4.10 Mb, with 66.8 mol% G + C content. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strains LB-2 and S. canadensis FWC47 were 77.8% and 21%, respectively. The predominant cellular fatty acids were summed feature 8 (Cω7c and/or Cω6c) and C. The major polar lipids were aminolipid, glycolipid, sphingoglycolipid, phosphatidylcholine, phosphatidylglycerol, four unidentified lipids, glycophospholipid, phosphatidylethanolamine and diphosphatidylglycerol. The predominant respiratory quinone was Q-10 and the major polyamine was sym-homospermidine. On the basis of phenotypic, genotypic and phylogenetic evidences, strain LB-2 represents a novel species in the genus Sphingomonas, for which the name Sphingomonas caeni sp. nov. is proposed. The type strain is LB-2 (GDMCC 1.3630 = NBRC 115,102).