Biodegradation of chlorpyrifos and its hydrolysis product 3,5,6-trichloro-2-pyridinol using a novel bacterium Ochrobactrum sp JAS2: A proposal of its metabolic pathway

Biodegradation of chlorpyrifos and its major metabolite 3,5,6-trichloro-2-pyridinol (TCP) were studied with a novel bacterial strain JAS2 isolated from paddy rhizosphere soil. The molecular characterization based on 16S rRNA gene sequence homology confirmed its identity as Ochrobactrum sp. JAS2. The JAS2 strain degraded 300 mg l(-1) of chlorpyrifos within 12 h of incubation in the aqueous medium and it produced the TCP metabolite. However, after 72 h of incubation TCP was also completely degraded by the JAS2 strain. A tentative degradation pathway of chlorpyrifos by Ochrobactrum sp. JAS2 has been proposed on basis of GC-MS analysis. The complete degradation of chlorpyrifos occurred within 24 h in the soil spiked with and without addition of nutrients inoculated with Ochrobactrum sp. JAS2. TCP was obtained in both the studies which was degraded completely by 96 h in the soil spiked with nutrients and whereas 120 h in absence of nutrients in the soil. The mpd gene which is responsible for organophosphorus hydrolase production was identified. The isolates Ochrobactrum sp. JAS2 also exhibited a time dependent increase in the amount of tricalcium phosphate solubilization in Pikovskaya's medium. Further screening of the strain JAS2 for auxiliary plant growth promoting activities revealed its remarkable capability of producing the indole acetic acid (IAA), hydrogen cyanide (HCN) and ammonia. (C) 2015 Elsevier Inc. All rights reserved.