Bacillus Thuringiensis Kurstaki Research Articles

Effect of Bacillus thuringiensis Berliner on prepupal and pupal stages of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

The prepupal stage of Spodoptera littoralis was affected by Bacillus thuringiensis kurstaki HD-1 (Dipel) at high concentration (5%), when sprayed or kept in soil treated with the pathogen. The emerged moths showed a short longevity associated with low egg production and low fertility. Increase in malformed individuals was observed. Treatment of the pupae of S. littoralis with B. thuringiensis during different ages showed an increased effect when treatment was applied, immediately after pupation.

Effects of the three proteases from gut juice of the silkworm, Bombyx mori, on the two morphologically different inclusions of .DELTA.-endotoxin produced by Bacillus thuringiensis kurstaki HD-1 strain.

Three proteases designated P-I, P-II, and P-III were separated from larval gut juice of the silkworm, Bombyx mori, and the effects of these proteases on the two morphologically different inclusions produced by Bacillus thuringiensis kurstaki HD-1 strain were investigated. Bipyramidal inclusions were solubilized by each protease at pH 10.2, and proteins with a molecular weight of about 60,000 were produced, while cuboidal inclusions were resistant to the proteases. Protease P- III appeared to be most important in the dissolution of the bipyramidal inclusions. Based on the affinity to various synthesized substrates, P-III was considered to be a chymotrypsin-like protease. After dissolution of inclusions by P-III, dissolved and undissolved fractions were separated, and the insecticidal activity of each fraction was tested. Results indicate that bipyramidal inclusions are preferentially toxic to the silkworm and the cuboidal ones carry the mosquitocidal activity.

Insecticidal activity of bipyramidal and cuboidal inclusions of .DELTA.-endotoxin and distribution of their antigens among various strains of Bacillus thuringiensis.

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 subunit 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.