Overproduction of Encapsulated Insecticidal Crystal Proteins in a Bacillus thuringiensis spoOA Mutant


The spoOA gene of Bacillus subtilis encodes the key factor involved in the initiation of sporulation. It was previously shown that the B. thuringiensis (Bt) cryIIIA gene, encoding a toxin active against coleopteran larvae, is overexpressed in an spoOA mutant of B. subtilis. In this paper we describethe construction of a Bt spo0A mutant strain and its use to produce insecticidal crystal proteins. The spoOA gene of Bt was cloned and identified by its ability to transform a B. subtilis spoOA mutant to prototrophy. Its nucleotidesequence is homologous to the B. subtilis gene. The spo0A gene was replaced in the Bt genome with a dis rupted copy to give an Spo- strain unable to initiate sporulation. When the cryIIIA gene was cloned in the Bt spoOA mutant, large amounts of toxins were produced and accumulated to form a large crystal inclusion which remained encapsulated within the ghost cell. These encapsulatedtoxins were highly active against coleopteran larvae. We anticipate that the cryIIIA expression system and the Bt spoOA mutant will provide a convenient process to generate novel formulations of stabilized and environmentally safe Bt-based biopesticides.

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Correspondence to Didier Lereclus.

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Lereclus, D., Agaisse, H., Gominet, M. et al. Overproduction of Encapsulated Insecticidal Crystal Proteins in a Bacillus thuringiensis spoOA Mutant. Nat Biotechnol 13, 67–71 (1995). https://doi.org/10.1038/nbt0195-67

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