Mating between Bacillus subtilis and Bacillus thuringiensis and transfer of cloned crystal genes

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We took advantage of the recently discovered high frequency transfer of plasmids between strains of B. thuringiensis to obtain the heterospecific mating between a Bacillus subtilis strain, which contained the plasmid crystal gene from strain berliner 1715, and different B. thuringiensis strains. The plasmid-coded crystal gene was inserted in the plasmid pBT 42-1 and introduced into an acrystalliferous B. thuringiensis strain where it promoted the synthesis of the crystal protein. The plasmid was maintained stably and allowed the synthesis of a toxic parasporal body. The plasmid pBT 42-1 was also introduced into a wild-type strain israelensis and the transcipient strains produced both types of δ endotoxin, which are active on both lepidopteran and dipteran larvae. The transfers were also performed using the cloned crystal gene of chromosomal origin, but in this case, the gene was integrated into the chromosomal DNA of the transcipient strains and did not seem to be expressed.