Assignment of the δ‐endotoxin gene of Bacillus thuringiensis var. israelensis to a specific plasmid by curing analysis

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Abstract
Plasmid analysis of Bacillus thuringiensis var. israelensis revealed the presence of at least 9 plasmids. A high frequency of plasmid loss occurred when this organism was grown at elevated temperature (42°C). Analysis of over 100 isolates cured of one or more plasmids by this method revealed that loss of a 72 MDa plasmid was invariably accompanied by loss of the ability to synthesize the insecticidal δ‐endotoxin protein. Deletion of any of the other plasmids had no effect on δ‐endotoxin production. These results indicate the presence of a plasmid‐coded copy of the structural gene for the insecticidal δ‐endotoxin in B. thuringiensis var. israelensis.