A bacteria strain, YW6, capable of utilizing monocrotophos (MCP) as the sole carbon and nitrogen sources for growth was isolated from paddy soil and identified as Starkeya novella. Strain YW6 completely degraded 0.2 mM MCP within 36 h without any lag period. Addition of carbon source resulted in slowing down of the initial rate of degradation of MCP, while the presence of a more favorable source of nitrogen enhanced the degradation of MCP. In addition to the degradation of MCP, strain YW6 was also able to degrade a wide range of organophosphorus pesticides (OPs) containing P-O-C bond, but not dimethoate, which has P-S-C bond. A MCP degradation pathway was proposed on the basis of metabolite production patterns and identification of the metabolites. MCP is hydrolyzed at the P-O-C bond to form N-methylacetoacetamide and dimethyl phosphate; N-methylacetoacetamide is transformed to N-methyl-4-oxo-pentanamide, which was subsequently converted to 5-(methylamino)-5-oxo-pentanoic acid, and 5-(methylamino)-5-oxo-pentanoic acid is cleaved to glutaric acid and methylamine. These findings provide new insights into the microbial metabolism of MCP. To the best of our knowledge, this is the first report on the degradation of MCP by Starkeya bacteria.
Keywords: Degradation pathway; MCP; Metabolite; Monocrotophos; Organophosphorus pesticide; Starkeya novella YW6.