Enhanced Biodegradation of 2,3,4,5,6-pentachlorocyclohexan-1-ol -- a b-HCH Metabolite -- in the Presence of a and g-HCH Isomers by Pseudomonas aeruginosa ITRC-5
A. Singh, A. Kumar, K. Misra
Rice University, US
Keywords: pseudomonas aeruginosa ITRC-5, b-Hexachlorocyclohexane, 2, 3, 4, 5, 6-pentachlorocyclohexan-1-ol, biodegradation
Abstract:Chlorinated insecticide hexachlorocyclohexane (HCH), which is still used in many countries in agriculture and forestry, leads to environmental problems. HCH consists of a mixture of four isomers: a-, b-, g-, and d. Efforts have been made for the remediation of soils and groundwater contaminated with the toxic and persistent HCH isomers through biodegradation processes. A bacterium pseudomonas aeruginosa ITRC-5 degrades not only a-, g-, and d- HCH isomers of but also b-HCH which is the most recalcitrant due to its chemical stability. The degradation of b-isomer is accompanied with the formation of a metabolite 2,3,4,5,6-pentachlorocyclohexan-1-ol (PCCOL). In the present study, effectiveness of ITRC-5 strain in further degradation of PCCOL was evaluated. g-HCH grown ITRC-5 cells show higher degradation of PCCOL than the t-HCH grown cells do. Furthermore, degradation of PCCOL by g-HCH grown cells is enhanced in the presence of a- or g-HCH isomers. Cloned genes of ITRC-5 bacterium showed 50% degradation of PCCOL in 16 hrs. The ITRC-5, therefore, demonstrates potential for the bioremediation of b-HCH and PCCOL.