Caharacterization and determination of insecticidal features of Bacillus thuringiensis isolated from natural environment

Characterization and Determination of Insecticidal Features of Bacillus thuringiensis Isolated from Natural Environment In the present study, 3 isolates [(BnBt (Balaninus nucum, adult), Mm2 (Melolonta melolanta, adult) and MnO {Malacosoma neustria, larvae)] obtained from insects and 6 isolates [(isolate 6 from Çağlayan, isolate 11 from Yeşilova, isolate 27 from Akçaabat, isolates 29 and 40 from Tonya and isolate 46 from Çaykara)] obtained from soil samples were characterized based on their phenotypic, molecular and chemotaxonomical features. According to light and scaning electron microscopy results, six isolates (BnBt, MnÖ, 27, 29, 40 and 46) have bipyramidal, one isolate (6) has spherical, one isolate (Mm2) has flat square, and one isolate (11) has irregular shape crystal. Based on the ISR- PCR results, B. thuringiensis isolates formed identical bands with the control B. thuringiensis isolates. PCR analyses have shown that BnBt, MnO, 1 1 and 29 have cryl and cry2 genes. On the other hand, Mm2 and 6 contain cry3 and cry4 genes, respectively. SDS- PAGE analyses have shown that isolates contain protein components with molecular masses ranging from 65-130 kDa. After trypsin digestion of solubilized crystals, SDS- PAGE resolved trypsin-resistant peptides ranged between 50 and 65 kDa. The plasmid DNA contents of the isolates were compared with control B. thuringiensis strains. Based on these results 4-8 plasmids were detected at all isolates pxpect 11. Toxicity tests have shown that BnBt and MnO have insecticidal effect against Malacosoma neustria and Lymantria dispar, isolate Mm2 has been found to be toxic to Leptinotarsa decemlineata mdAgelastica alni. However, no insecticidal activity has been found in the other isolates. In conclusion, isolates BnBt and MnO are similar to Bacillus thuringiensis subsp. kurstaki, isolates Mm2 and 6 are identical to Bacillus thuringiensis subsp. tenebrionis and Bacillus thuringiensis subsp. israelensis, respectively. The other isolates are thought to be new B. thuringiensis isolates. Key Words: Bacillus thuringiensis, Crystal Proteins, cry Genes, Biological Control