Of newly isolated colonies with the appearance of Bacillus thuringiensis, 47.5% were found to produce the parasporal crystals characteristic of this species. These positive isolates were screened using the polymerase chain reaction for their possession of a gene encoding a specific protoxin type, CryIB. Strains with and without this gene were screened for their ability to produce β-exotoxin and Bacillus cereus-type enterotoxin. It was found that 35% of the isolates possessed the cryIB gene; of these 83% also produced enterotoxin and 58% produced β-exotoxin. No statistical significance was found for linkage between any of these characteristics. The probability, therefore, of isolating a strain of B. thuringiensis which specifically possessed the cryIB gene but did not produce either of the other, undesired, toxins, from the soil sample used, was 1.2%.
Perani, M., Bishop, A. H., & Vaid, A. (1998). Prevalence of β-exotoxin, diarrhoeal toxin and specific δ-endotoxin in natural isolates of Bacillus thuringiensis. FEMS Microbiology Letters, 160(1), 55–60. https://doi.org/10.1016/S0378-1097(98)00010-X