Protein Profiling of Bacillus thuringiensis Isolated from Agro-forest Soil in Bangladesh

Bacillus thuringiensis (Bt) is a soil bacterium possessing insecticidal characteristics. The aim of the present study was to isolate and characterize Bt strains from the local agro forest soil in Bangladesh. Bt was isolated from 53 soil samples from diverse agro forest fields, and was subjected to further morphological and biochemical characterization. 47 isolates were presumptively confirmed as Bt. All the isolates showed parasporal crystal structure. All of them were resistant to 7% NaCl and 0.001% lysozyme and were motile, haemolytic, lecithinase producer, proteolytic and were unable to survive at 50?C. All of them were able to ferment glucose, maltose and trehalose but did not ferment arabinose, mannitol, sorbitol, xylose, lactose or rhamnose. All the isolates were sensitive to Chloramphenicol, Doxycycline, and Imipenum, whereas they were resistant to Penicillin G and Ampicillin. A study of virulence was also performed whereby 30 isolates were found to exhibit virulence properties. Surface protein analysis by 12% SDS-polyacrylamide gel electrophoresis (PAGE) revealed similar banding patterns as compared to reference strains of Bt (B. thuringiensis subsp. kurstaki HD-73, B. thuringiensis subsp. sotto and B. thuringiensis subsp. japonensis) which further confirmed the identity of the isolates as Bt. In toxin protein analysis by 7.5% SDS-PAGE, molecular weight of the dominant protein band was found to be 140-130 kDathis protein was assumed to be Cry 1 protein. The second most dominant protein with a molecular weight of 70-65 kDa resembled Cry 2 protein, and the third most abundant protein (75 kDa) mimicked the Cry 3 protein. Thus the Bt isolates were shown to produce different classes of Cry proteins, which may confer commercial applications in agriculture. Growth optimization and formulation conditioning research may lead the isolates to be identified as potential strains for bio-insecticide production for use in Bangladesh and beyond