Study on Imidacloprid Induced Intoxication and Its Biodegradation by Soil Isolate Bacillus weihenstephanensis

Aims: The study was conducted to investigate the effect of imidacloprid on biochemical parameters and soil isolate growth. The soil isolate was also studied for imidacloprid degradation.

Study Design: The soil isolate was identified and used for toxicity testing. The isolate of Bacillus weihenstephanensis was further tested for its ability to degrade imidacloprid in minimal salt medium (MSM) and tryptic soya medium (TSB). The role of plasmid in imidacloprid degradation was established by curing experiments.

Place and Duration of Study: Department of Biotechnology and Microbiology, Karnatak University, Dharwad, India between June 2011 and December 2012.

Methodology: The soil isolate was identified by morphological, biochemical characters and 16s rDNA identification. Effect of imidacloprid on DNA, RNA, protein, glucose and growth in soil isolate was studied with 10-3 to 10-7 molar imidacloprid for 96 h. Imidacloprid degradation was determined in MSM and TSB for 28 days with samples taken on 7, 14, 21 and 28th day. The insecticide concentration was tested by HPLC. Plasmid curing was performed.

Results: The soil isolate was identified as Bacillus weihenstephanensis. The study involving soil isolate Bacillus weihenstephanensis with 10-3 to 10-7 molar imidacloprid showed significant (P<0.05) decrease in content of DNA, RNA, protein, glucose and growth. Bacillus weihenstephanensis in MSM and TSB showed 46 and 78% imidacloprid degradation in four weeks. The plasmid of Bacillus weihenstephanensis was cured in fourth generation. 18.80% and 75% degradation observed in cured and non cure cells of Bacillus weihenstephanensis in TSB.

Conclusion: Study showed that imidacloprid affects the biochemical contents and intern growth of soil isolate Bacillus weihenstephanensis. Study also revealed that Bacillus weihenstephanensis was able to degrade imidacloprid in MSM and TSB. Further plasmid curing revealed that the genes for imidacloprid degradation are located both in plasmid and chromosome. The soil isolate was able to utilize imidacloprid as sole carbon and nitrogen source as indicated by its growth in MSM.