f Sphingobium barthaii sp. nov., a high molecular weight polycyclic aromatic hydrocarbon-degrading bacterium isolated from cattle pasture soil

A Gram-stain-negative, yellow, rod-shaped bacterium, designated strain KK22T, was isolated from a microbial consortium that grew on diesel fuel originally recovered from cattle pasture soil. Strain KK22T has been studied for its ability to biotransform high molecular weight polycyclic aromatic hydrocarbons. On the basis of 16S rRNA gene sequence phylogeny, strain KK22T was affiliated with the genus Sphingobium in the phylum Proteobacteria and was most closely related to Sphingobium fuliginis TKPT (99.8  %) and less closely related to Sphingobium quisquiliarum P25T (97.5  %). Results of DNA–DNA hybridization (DDH) revealed relatedness values between strain KK22T and strain TKPT and between strain KK22T and strain P25T of 21 ± 4  % (reciprocal hybridization, 27 ± 2  %) and 15 ± 2  % (reciprocal hybridization, 17 ± 1  %), respectively. Chemotaxonomic analyses of strain KK22T showed that the major respiratory quinone was ubiquinone Q-10, that the polar lipid profile consisted of phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, phosphatidyl-N-methylethylethanolamine and sphingoglycolipid, and that C18 : 1ω7c and C14 : 0 2-OH were the main fatty acid and hydroxylated fatty acids, respectively. This strain was unable to reduce nitrate and the genomic DNA G+C content was 64.7 mol%. Based upon the results of the DDH analyses, the fact that strain KK22T was motile, and its biochemical and physiological characteristics, strain KK22T could be separated from recognized species of the genus Sphingobium. We conclude that strain KK22T represents a novel species of this genus for which the name Sphingobium barthaii sp. nov. is proposed; the type strain is KK22T ( = DSM 29313T = JCM 30309T).