Plasmid profiling of indigenous Bacillus thuringiensis isolated from Tamil Nadu and Kashmir

Abstract

Bacillus thuringiensis cry genes are mainly present on megaplasmids. These genes code for crystal proteins which are toxic to insects. The present work aimed to study plasmid profiles of B. thuringiensis strains from different environmental zones. The plasmids were isolated by Reyes-Ramírez and Ibarra method using supplemented Spizizen broth. Different types of buffers (TES buffer pH 8.0; lysis buffer; SDS–TES buffer), sodium acetate (pH 4.8) and absolute ethanol were used during the plasmid extraction. Plasmid-enriched DNA pellet was dissolved in Tris–EDTA (pH 8.0), run in agarose gel and documented. Totally 35 B. thuringiensis strains were subjected to plasmid profiling. Different sizes of plasmids ranging from 108 kb to 2 kb in 97.22% strains were isolated. Out of 17 B. thuringiensis strains of plain areas, 88.23% had only one megaplasmid while as 11.76% had more than one plasmid. However 58.82% and 29.41% strains from hilly areas had shown one and more than one megaplasmids respectively. In B. thuringiensis strains from Tamil Nadu (Salem) plain areas with temperature range 18 °C–43 °C, 77.77% and 22.22% had shown single megaplasmids and more than one megaplasmid respectively. All B. thuringiensis strains from Kashmir plain areas with temperature range −6 °C to 37 °C had shown only one megaplasmid each. As megaplasmids usually harbor the crystal protein genes thus from our study it can be concluded that B. thuringiensis strains isolated from hilly areas with temperature range 13 °C–30 °C may contain more cry genes because of having more megaplasmid contents.