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Abstract
The insecticidal activities of 12 strains of Bacillus thuringiensis var. israelensis and purified delta-endotoxin crystals from the 4Q1 strain against mosquito larvae, Culex pipiens pallens, were measured and then compared with those of B. thuringiensis var. kurstaki and Bacillus sphaericus. Plasmid DNAs in acrystalliferous or crystalliferous strains of those bacteria and varieties were isolated and analyzed by agarose gel electrophoresis. There were at least 7 plasmids in the 4Q1 strain.
To determine the specific plasmid coding the mosquito-toxic endotoxin protein, the relationship between the activities and the plasmid patterns of those strains was investigated. The strains harboring the plasmid pBTI-6 NDA (70 megadaltons) had insecticidal activity even though they were acrystalliferous mutants, but all strains lacking the plasmid pBTI-6 DNA did not have the activity.