Abstract
A potential pesticide degrading bacterial isolate (2D), showing maximum tolerance (450 mg∙L-1) for cypermethrin, fipronil, imidacloprid and sulfosulfuron was recovered from a pesticide contaminated agricultural field. The isolate degraded cypermethrin, imidacloprid, fipronil and sulfosulfuron in minimal salt medium with 94, 91, 89 and 86% respectively as revealed by high performance liquid chromatography (HPLC) and gas chromatography (GC) analysis after 15 days of incubation. Presence of cyclobutane, pyrrolidine, chloroacetic acid, formic acid and decyl ester as major intermediate metabolites of cypermethrin biodegradation was observed in gas chromatography mass spectrometry (GC-MS) analysis. Results based on 16S rDNA sequencing, and phylogenetic analysis showed maximum similarity of 2D with Bacillus cereus (Accession ID: MH341691). Stress responsive and catabolic/pesticide degrading proteins were over expressed in the presence of cypermethrin in bacteria. Enzymatic kinetics of laccase was deduced in the test isolate under normal and pesticide stress conditions which suggested that the production of enzyme was induced significantly in pesticide stress (163 μg.μL-1) as compare to normal conditions(29 μg.μL-1) while the Km value was decreased in pesticides stress condition (Km = 10.57 mM) and increases in normal condition (Km = 14.33 mM).Amplification of laccase gene showed a major band of 1200bp. The present study highlights on the potential of 2D bacterial strain i.e., high tolerance level of pesticide, effective biodegradation rate, and presence of laccase gene in bacterial strain 2D, could become a potential biological agent for large-scale treatment of mixture of pesticide (cypermethrin, fipronil, imidacloprid and sulfosulfuron) in natural environment (soil and water).
Highlights
From the last 20th century the overall global production of grain has increased from 500 million tons to 700 million tons [1]
Four pesticide utilizing bacterial isolates were recovered from pesticide contaminated agricultural fields using plate assay
Gas chromatography (GC) results of standard of imidacloprid, fipronil and sulfosulfuron revealed the presence of major single peak of each pesticide at 4.3, 4.9, and 6.3 min respectively under optimized conditions of the instrument (S1A–S1C Fig)
Summary
From the last 20th century the overall global production of grain has increased from 500 million tons to 700 million tons [1]. India alone produces 250 million tons of grain but it losses 11 to 15% of total produced grains per year due to the pests attack and by some other causes [2] To prevent such losses and to achieve the food targets, farmers have adopted to use hybrid seeds, systematic irrigation and application of chemical fertilizers and pesticides [3,4]. Pesticides are developed under strict vigilance of regulatory authorities which regulate the production of pesticides and set guidelines for their use so to put least hazardous impact on human health and on their surrounding environment. Many environmental concern of pesticide has been already reported by researchers such as reducing biodiversity, nitrate leaching, decreased soil fertility, resistance in weed species towards common weedicides, increased cost of prevention and treatment endangering human health and acidification [9,10]
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