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

Abstract

A yellow-pigmented, hexachlorocyclohexane (HCH)-degrading bacterial strain, P25T, 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 15006T (97.7 %). The 16S rRNA gene sequence similarity between strain P25T 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 P25T and Sphingobium amiense IAM 15006T and other related strains was found be less than 30 %, confirming it to represent a novel species. The DNA G+C content of strain P25T was 65 mol%. The polyamine profile showed the presence of spermidine. The predominant cellular fatty acids were summed feature 8 (18 : 1ω7c and/or 18 : 1ω6c; 48.3 %), 16 : 0 (13.7 %) and 14 : 0 2-OH (8.8 %). The polar lipid profile of strain P25T 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 P25T 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 P25T (=MTCC 9472T =CCM 7543T).