Role of Gordonia sp JAAS1 in biodegradation of chlorpyrifos and its hydrolysing metabolite 3,5,6-trichloro-2-pyridinol

Abstract

Paddy field soil with prior exposure to chlorpyrifos was chosen for the biodegradation of the pesticide by employing bacteria with special emphasis given to actinomycetes. Actinomycetes are organisms predominantly known for their bioactive compounds, but there is dearth of work pertaining to their role in bioremediation. So this work was carried out to screen for actinomycetes and assess their potential in degradation of the pesticide. Actinobacterial strains were isolated from paddy field soil, with capabilities to degrade chlorpyrifos and its major metabolite 3,5,6-trichloro-2-pyridinol (TCP). Two strains were successfully isolated among which one strain was efficient and was able to tolerate high concentrations of chlorpyrifos. This strain was selected for further investigation; it was identified as Gordonia sp based on 16S rRNA analysis and designated as Gordonia sp JAAS1. The actinobacterial strain was able to degrade 110mgl(-1) of chlorpyrifos within 24h incubation, and TCP was found to accumulate in the culture medium. However, after 72h of incubation, TCP was degraded, and finally, diethylthiophosphoric acid (DETP) was obtained. Biodegradation of chlorpyrifos results in the formation of an antimicrobial compound 3,5,6-trichloro-2-pyridinol (TCP). It is more mobile compared with the parent molecule due to its higher water solubility thus, causing widespread contamination and has antimicrobial property. Therefore, biodegradation of TCP, the major metabolite of chlorpyrifos, is crucial as if left to accumulate, it will kill all the beneficial microbes in the soil. In this study, Streptomyces belonging to genus Gordonia sp JAAS1 strain capable of degrading not only chlorpyrifos but also TCP was observed. This is a first report pertaining to biodegradation of chlorpyrifos and its metabolite TCP from Gordonia genus. The ability to degrade chlorpyrifos and its metabolite TCP makes this strain a useful candidate for the remediation of contaminated sites.