Characterization of the delta-endotoxin of a Bacillus thuringiensis Isolate Active Against Tsetse, Glossina morsitans, and a Stem Borer, Chilo partellus
Titel:
Characterization of the delta-endotoxin of a Bacillus thuringiensis Isolate Active Against Tsetse, Glossina morsitans, and a Stem Borer, Chilo partellus
Auteur:
Osir, E. O. Vundla, W. R. M.
Verschenen in:
Biocontrol science and technology
Paginering:
Jaargang 9 (1999) nr. 2 pagina's 247-258
Jaar:
1999-06-01
Inhoud:
The delta-endotoxin crystals of a Bacillus thuringiensis isolate active against the tsetse fly, Glossina morsitans, were isolated from a nutrient broth culture by low speed centrifugation. Analysis of these crystals by denaturing gel electrophoresis revealed that the major component of the crystal delta-endotoxin was a protein of mol. wt ~ 120000. Upon solubilization under alkaline pH and reducing conditions, the crystal yielded a toxin of mol. wt ~ 64 000. Treatment of the toxin with bovine trypsin resulted in a shift in the mol. wt to a toxin of ~ 62000, while treatment with bovine chymotrypsin gave a toxin of ~ 60 000. Methyl green staining revealed that the endotoxin was phosphorylated, while staining with periodic acid schiff reagent showed that it was glycosylated. The carbohydrate moiety was of the high mannose type as shown by staining with fluorescein isothiocyanate conjugated to concanavalin A. Following gel permeation chromatography on a Superose 12 column, the solubilized toxin resolved into six main protein peaks, two of which had trypsin-like activity. The delta-endotoxin caused mortalities in the tsetse, G. morsitans morsitans (LC50 of 42.4mug ml-1) and 4th instar Chilo partellus larvae (LC50 of 53.8 mug ml-1), but had no effect on 3rd instar Aedes aegypti larvae.
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