Comparaison des profils plasmidiques de mutants oligosporogènes chez Bacillus thuringiensis var. kurstaki HD-1 après traitement à l'ozone et à la nitrosoguanidine

Two strains of Bacillus thuringiensis were used in order to isolate sporeless and crystalliferous mutants. These strains, B. thuringiensis var. kurstaki HD-1 and var. israelensis Q-2, produce a crystalline inclusion, δ-endotoxin, which is lethal for lepidopteran and dipteran larvae, respectively. Mutants derived from strain HD-1 were easily isolated because of their characteristic morphology. By comparing different plasmidic patterns of the strains, we can confirm the relationship existing between a DNA extrachromosomic element and the production of δ-endotoxin in B. thuringiensis. However, the absence of toxic crystallin protein does not necessarily mean that all plasmids are absent.Key words: Bacillus thuringiensis, oligosporogenous, ozone, nitrosoguanidine, plasmids.