Isolation, characterization and serotype classification of Bacillus thuringiensis from different soil samples of Fars province

Bacillus thuringiensis (Bt) is a bacterium best known for its production of crystal-like bodies comprised of one or more crystal proteins in sporulation phase, which can be toxic to insects, nematodes and cancer cells. The purpose of this study is isolation, characterization and comparison of Cry proteins in the isolated strains obtained in different parts of Fars province. 25 soil samples were collected from six different habitats in Fars province using seven different methods. Characterization was performed based on biochemical tests, protein crystal morphology by phase-contrast microscope and variation of cry protein toxin using SDS-PAGE. The tests showed a highest count of Bt strains in soil samples obtained from Shiraz city. The Bt colonies were classified according to biochemical tests such as: sucrose and salicin fermentation, lecithinase production and esculin hydrolyzing. Results showed that although isolated strains have a variety of protein bands with different sizes, the proteins with 34KD was observed following proteinase K digestion in all the samples.