Synergistic Biodegradation of Monocrotophos and Plant Growth Stimulation by Soil Bacterial Strains

Monocrotophos (MCP) is a widely used insecticide in agriculture, but its high toxicity poses significant environmental and health risks. The biodegradation of monocrotophos by indigenous microbes is crucial in reducing its toxicity. The present study was aimed at assessing plant growth- stimulating factors and the biodegradable ability of monocrotophos of two indigenous soil bacterial strains, CAB1 and SD8, isolated from monocrotophos-contaminated agricultural soils in Mysuru and Mandya, Karnataka, India. Biodegradation was evaluated using spectroscopy and chromatography, with substrate degradation confirmed by the disappearance of the main peak in HPLC profiles and intermediate metabolites identified through FTIR and LC-MS analyses. Molecular characterization identified CAB1 as Stenotrophomonas pavanii (OQ861163) and SD8 as Brevibacillus parabrevis (OQ881083). Results showed that the two bacterial strains utilized MCP as their sole carbon source and exhibited biodegradation rates of 88% and 90%, respectively, under optimal conditions. Results further showed that S. pavanii CAB1 and B. parabrevis SD8 produced ammonia, IAA, catalase, and cellulase, and demonstrated phosphorus and zinc solubilization. The degradation ability of CAB1 and SD8 is attributed to the presence of the opd gene and the opdA gene. Trimethyl phosphate, dimethyl phosphate, cyclohexanone, 2- cyclohexylidene, oxalic acid, and isohexyl pentyl esters were the non-toxic intermediates produced during the biodegradation of MCP. The strains S. pavanii CAB1 and B. parabrevis SD8 can be employed, alongside a microbial consortium formulation, for the detoxification of hazardous pollutants in contaminated soils and promotion of plant growth.