Soil enrichment and dominant occurrence of Bacillus thuringiensis subsp. israelensis in a garden sprayed with Bacillus thuringiensis based biopesticide

Aims: Bacillus thuringiensis (Bt) based biopesticides have been successfully used to control agricultural pests and vectors of human diseases. B. thuringiensis subsp. israelensis (Bti) based formulations have been used as anti-dipteran agents to control the mosquito larvae. The study was conducted to understand the occurrence and relative dominance of Bti in a botanical garden, a non-agricultural ecosystem previously sprayed with Bt based formulation. Methodology and results: The preliminary phenotypic investigations revealed that all the isolates were Bt. The Coomassie Brilliant Blue staining of the isolates revealed the presence of spherical crystals, a striking characteristic of Bt. The SDS-PAGE analysis provided basic information on the similarity of all the isolates based on the protein profile. The similarity between native isolates and Bti was further confirmed by RAPD-PCR. Conclusion, significance and impact study: Through phenotypic and molecular methods, this study has conclusively proved the occurrence and the dominance of Bt isolates similar to the Bti used for spraying. This study provided new insight into the possible mechanism exerting continued pressure on the target insects, natural cry gene transfer because of the dominant presence.