Sphingobium quisquiliarum sp nov., a hexachlorocyclohexane (HCH)-degrading bacterium isolated from an HCH-contaminated soil

A yellow-pigmented, hexachlorocyclohexane (HCH)-degrading bacterial strain, P25(T), was isolated from an HCH dump site located in the northern part of India. Phylogenetic analysis based on the 16S rRNA gene sequence showed that the strain belongs to the genus Sphingobium, as it showed highest sequence similarity to Sphingobium amiense IAM 15006(T) (97.7%). The 16S rRNA gene sequence similarity between strain P25(T) and members of other species of the genus Sphingobium with validly published names ranged from 94.0 to 97.7%. The DNA-DNA relatedness between strain P25(T) and Sphingobium amiense IAM 15006(T) and other related strains was found be less than 30%, confirming it to represent a novel species. The DNA G + C content of strain P25(T) was 65 mol%. The polyamine profile showed the presence of spermidine. The predominant cellular fatty acids were summed feature 8 (118:1 omega 7c and/ or 18:1 omega 6c; 48.3%), 16:0 (13.7%) and 14:0 2-OH (8.8%). The polar lipid profile of strain P25(T) also corresponded to those reported for sphingomonads (phosphatidylethanolamine, diphosphatidylglycerol, phosphatidyldimethylethanolamine, phosphatidylglycerol, phosphatidylcholine, sphingoglycolipid), supporting its identification as a member of the family Sphingomonadaceae. The results obtained from DNA-DNA hybridization and biochemical and physiological tests clearly distinguished strain P25(T) from closely related members of the genus Sphingobium. Thus, a novel species of the genus Sphingobium is proposed, Sphingobium quisquiliarum sp. nov. The type strain is P25(T) (=MTCC 9472(T) =CCM 7543(T)).