Background & aim: Bacillus thuringiensis (Bt) is a Gram-positive and sporulating bacteria. The main habitat of the bacteria is soil and able to produce a wide variety of insecticidal crystal protein's with Insecticide properties. The aim of the study was to detection of cry1, cry2, cry3, cry4 and cry5 genes in the B. thuringiensis isolated from soil samples by Multiplex-PCR method.

Methods: In this cross-sectional study, 200 grams of soil sample randomly were collected from at 10 cm depth and totally 100 soil samples were taken from different areas of Tehran, Iran. According to the protocol approved by WHO, suspected colonies on B. thuringiensis isolated and strains were confirmed by the microbiological and biochemical tests. After DNA extraction Multiplex-PCR using specific primers in thermal cycler gradient the presence of cry genes were confirmed. Data were analyzed using one-way ANOVA.

Results: Out of 100 soil samples studied, 41 strains were confirmed as B. thuringiensis. MPCR results showed that 14 strains carrying the crystalline toxin, 7 strains (50%) cry1, 4 strains (5.28%) cry2 and 3 strains (5.21%) cry3 genes. Cry4 and cry5 genes were not observed in any isolates (0.0%).

Conclusion: Based on great diversity of crystal protein genes and the absence of reliable phenotypic methods for detection of the presence of crystal proteins, simultaneous identification of these genes can be found as low cost and high speed response for identification of crystalline genes produced by B. thuringiensis.