Isolation and characterization of indigenous bacterial assemblage for biodegradation of persistent herbicides in the soil

Abstract

Extensive pesticides (herbicides) use is nega-tively disturbing the environment and humans. Pesticide bioremediation with eco-friendly techniques bears prime importance. This study aimed to isolate and characterize three different herbicides (metribuzin, clodinafop-prop-argyl, MCPA (2-methyl, 4 chlorophenoxyacetic acids) and Bromoxynil) degrading bacterial strains from agricultural fields of Punjab University, Pakistan. Among the 12 bacterial isolates, 5 were metribuzin degrading, 3 were clo-dinafop propargyl degrading and, 4 were MCPA and Bro-moxynil degrading bacteria. Morphological, microscopic, and molecular characterization revealed that the major-ity of these bacterial strains were gram-negative and be-longed to Bacillus and Pseudomonas genera. The isolates A6, B3, and C1 were subjected to respective herbicide degradation and the data was confirmed through GC-MS analysis. The effect of herbicide concentrations, pH, and temperature on bacterial growth was determined at OD600. The strain A6 degraded 14.8% metribuzin out of the provided concentration of 50 ppm by following the deamination pathway. While the isolates B3 and C1 degraded 23.2% and 33.9% clodinafop, MCPA and bromo-xynil, respectively, at a spiking concentration of 50ppm. The clodinafop, MCPA & Bromoxynil were metabolized into less toxic products i.e., dicarboxylic acids and 2-me-thyl phenol respectively, and metabolized via decar-boxylation and dehalogenation mechanism. The pre-sent study evaluates the herbicides degrading bacterial strains that could potentially be used for bioremediation of agricultural contaminated sites.