[Detection of some toxin genes related to pathogenicity in Bacillus cereus group strains]

Bacillus thuringiensis is a member of the B. cereus group, which also contains B. cereus, B. mycoides, B. pseudomycoides , B. anthracis and B. weihenstephanensis. Among them, B. thuringiensis and B. cereus share a high level chromosomal similarity and are phenotypically similar except that B. thuringiensis has insecticidal plasmid encoding crystal proteins. Twenty-six B. cereus group strains were surveyed in this study for the presence of enterotoxin genes and other toxin genes related to pathogenicity. PCR results showed that the pleiotropic virulence regulator plcR was presented in 17 B. cereus group strains. About 73% of the B. cereus group strains and 83% of the B. thuringiensis strains contained at least one of the three hbl genes and one of the three nhe genes, indicating that B. thuringiensis, including strains used commercially, had enterotoxin encoding genes. Additionally, B. cereus DBt248 was proved to be devoid of all three hbl genes, three nhe genes or plcR. Thus this strain might be a potential candidate as a host strain for expressing B. thuringiensis crystal toxins to construct safety insecticidal engineering strains without enterotoxic activity.