Insecticidal Activity of Bipyramidal and Cuboidal Inclusions of δ-Endotoxin and Distribution of Their Antigens among Various Strains of Bacillus thuringiensis

Abstract

Bacillus thuringiensis kurstaki strain HD-1 produces two morphologically different parasporal inclusions of δ-endotoxin, bipyramidal and cuboidal inclusions. We found that the bipyramidal inclusion was composed of a 130, 000-dalton sub)unit protein and was toxic to the silkworm, Bombyx mori (a lepidopteran insect), but not to the mosquito, Aedes aegypti (a dipteran insect) and that the cuboidal inclusion was composed of a 65, 000-dalton subunit protein and was associated with the mosquitocidal activity. The distribution of the two proteins, the toxic fragment with a molecular weight of about 60, 000 derived from the bipyramidal inclusions and the cuboidal toxin, was studied in various strains of B. thuringiensis by an enzyme-linked immunosorbent assay.