DISCRIMINATION BETWEEN BACILLUS-CEREUS AND BACILLUS-THURINGIENSIS USING SPECIFIC DNA PROBES BASED ON VARIABLE REGIONS OF 16S RIBOSOMAL-RNA

Identification of Bacillus cereus and differentiation between B. cereu s and closely related species are currently based on biochemical tests . The main problem is to discriminate between B. cereus and B. thuring iensis. Sequencing part of the 16S rRNA showed that several B. cereus isolates present in food and involved in food poisoning, confirmed acc ording to the classical biochemical methods, were in fact B. thuringie nsis. As this organism is the most commonly used microbial insecticide worldwide, the results of this study emphasize the need for accurate identification methods and for careful screening of strains for use as insecticides. Therefore, specific DNA probes based on the variable re gion V1 of 16S rRNA of B. cereus and B. thuringiensis were designed. T he probes were used in hybridization experiments with the variable reg ion amplified using the polymerase chain reaction. In this way, a rapi d and sensitive method was developed to distinguish B. cereus and B. t huringiensis.