Molecular study of the pesticides degradation pathways in actinobacterias and their use in bioremediation processes

SINELI, P; DAVILA COSTA, JOSE; TORTELLA, GONZALO; RUBILAR, O; CUOZZO, S

Workshop; 5 th International Wokshop advances in Science and technology of bioresouces; 2015

Hexachlorocyclohexane (HCH) is a highly toxic and persistent organochloride pesticide that has caused serious environmental problems since it began to be produced at the beginning of the 1940s. During the synthesis process of HCH different isomers are produced. All HCH isomers have the same molecular formula 1,2,3,4,5,6-HCH, but are differentiated by variations in the axial-equatorial positions of the molecules of chlorine around a ring of 6 carbons. Of all the isomers, only γ-HCH (lindane) possesses insecticidal activity; however the other isomers are still toxic for humans. It was observed that actinobacterias: Streptomyces sp. A2, A8 and M7 were able to grow 2.5, 1.5 or 1.4 times more than in the presence of α-HCH as the only carbon source. When β-HCH was added, Streptomyces sp. A2, and M7 were capable to grow 1.5 times more than in control cultures. In other experiment in the presence of γ-HCH as the only carbon were detected in cell-free extracts γ-pentachlorocyclohexene and 1,3,4,6-tetrachloro-1,4-cyclohexadiene, both being products of the dechlorinase activity. As well as Pentachlorocyclohexenes and tetrachlorocyclohexenes were detected as metabolites in the presence of α- and β-HCH, while no phenolic compounds were found. In conclusion, we have demonstrated that Streptomyces sp. M7 can degrade α- β- and γ-hexachlorocyclohexane and could be considered as a potential agent for bioremediation of environments contaminated by organochlorine. This is the first time that the presence of an enzyme with dechlorinase activity has been demonstrated in an actinomycete strain, where actinobacteria can grow in presence of HCH-isomers. It is important to notice that β-HCH, is the most recalcitrant. For this reason actinobacteria could be considered as promising strains for HCH isomers degradation from contaminated areas.