Loren I. Davidson

Purification of the insecticidal toxin from the parasporal crystal of Bacillus thuringiensis subsp. kurstaki.

Abstract The insecticidal toxin of Bacillus thuringiensis subsp. kurstaki was isolated from parasporal crystals. The toxin, which is stable for several months, is a glycoprotein with an apparent molecular weight of 68,000 that is generated upon solubilization and activation of a higher molecular weight protoxin (MWapp = 1.3 × 105) at alkaline pH. The toxin was purified by gel filtation and anion exchange chromatography and its molecular weight was established by gel filtration chromatography and SDS polyacrylamide gel electrophoresis.

Specificity of cultured insect tissue cells for bioassay of entomocidal protein from Bacillus thuringiensis.

SummaryCultured tissue cells from lepidopteran and dipteran sources displayed an order-specific response to entomocidal protein from crystals ofBacillus thuringiensis. Protein isolated from crystals ofB. thuringiensis subsp.kurstaki was effective against cells of the spruce budworm (Choristoneura fumiferana) and the tobacco hornworm (Manduca sexta), but was inactive against both mosquito cell lines tested (Aedes aegypti andAnopheles gambiae). Conversely, protein from inclusion bodies ofB. thuringiensis subsp.israelensis was fully active only against the mosquito cell lines but displayed reduced (four- to seven-fold) toxicity for the lepidopteran cell lines. One exception to this pattern of specificity was observed with aPlodia interpunctella cell line, which failed to respond to either crystal protein preparation. The moth toxin was stable at 4° C for months, whereas the mosquito toxin was susceptible to proteolytic degradation and was unstable for periods longer than 2 wk.

Characterization of spore coat proteins of Bacillus thuringiensis and Bacillus cereus

Abstract 1. 1. Spore coat extracts from Bacillus thuringiensis subspecies kurstaki and israelensis and Bacillus cereus T and B. cereus NRRL 569 were characterized by polyacrylamide gel electrophoresis in sodium dodecyl sulfate and by amino acid analysis. 2. 2. Both B. cereus spore coats had similar electrophoretic profiles. 3. 3. The B. thuringiensis spore coats contained crystal proteins as major components as well as lower mol. wt proteins. 4. 4. B. thuringiensis subsp. israelensis had a unique coat protein profile which was different from B. cereus and B. thuringiensis subsp. kurstaki coats. 5. 5. Insecticidal activity of spores against the tobacco hornworm, Manduca sexta, and the mosquito, Aedes aegypti, also was determined. 6. 6. B. thuringiensis subsp. kurstaki spores were lethally toxic to the tobacco hornworm (Lepidoptera) larvae, whereas spores of the other subspecies were not. 7. 7. Except for subspecies israelensis, none of the spores was effective against the mosquito (Diptera) larvae.