A Genomic and Functional Analysis of Bacterial Diversity in Agricultural Soil for Chlorpyrifos Biodegradation
Islam, Nelufa Yesmin
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Chlorpyrifos (CP) is a widely used organophosphate (OP) insecticide and a potent environemntal neurotoxin. This research project focuses on the potential of bacteria, both native to agricultural soil and part of a designed consortium composed of Iyer laboratory strains, to completely degrade CP and its toxic byproducts in different types of agricultural soil. Sequence data from isolated agricultural microorganisms was analyzed using the RAST (Rapid Annotation using Subsystem Technology) server to identify putative CP degradation biomarkers. Metabolite production and degradation kinetics analysis gas chromatography mass spectrophotometry (GCMS) analysis was conducted on each soil sample and compared to soil spiked with different combinations of bacterial consortia over a period of 7 days to determine the effectiveness of CP degradation in non-augmented and augmented soil. Genomic analysis of ranch, garden and crop soil microorganisms revealed multiple CP degradation biomarkers including a family of diverse OPHC2-like metallo-β-lactamase (MBL) enzymes, and 3-oxoadipate enol-lactonases. GCMS analysis of these soil samples inoculated with CP support putative microbial degradation activity show that 4 CP metabolites are consistently released including 3,5,6-trichloropyridinol (TCP), phosphorothioic acid, fumaric acid and ethanol. Non-augmented ranch soil and crop field soil display a greater degradation capacity than garden soil possibly due to greater CP pesticide exposure at these sites. Overall, degradation kinetics for augmented and non-augmented soil samples was 0.79d-1 and 0.19d-1 and half-life 1.03 and 5.45 days respectively. CP inoculated soil spiked with a bacterial consortium consisting of all 3 strains exhibited the highest degradation rate with 78.55% of CP degraded after 48 hours. The outcome of this study suggests that while native agricultural populations are capable of low-level CP degradation, supplementing contaminated soil with a bacterial consortium consisting of Pseudomonas putida, Ochrobactrum anthropi and Rhizobium radiobacter could be a highly effective and safe biological approach to facilitating rapid CP degradation.