Isolation of Bacillus thuringiensis from Stored Tobacco and Lasioderma serricorne (F.)

Bacillus thuringiensis was isolated from dried tobacco residues and dead tobacco beetles (Lasioderma serricorne (F.); Coleoptera: Anobiidae) collected in a large number of locations worldwide. Eighty-eight samples of stored tobacco were analyzed and yielded 78 B. thuringiensis strains which were characterized on the basis of parasporal crystal morphology, sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles, and the results of an immunoblot analysis of the insecticidal crystal proteins. Flagellar antigen identification was used to differentiate selected isolates. Strains that produced rhomboidal crystals associated with the Coleoptera-specific pathotype (Cry III group) were the most abundant strains (59% of the isolates). Preliminary toxicity assays were performed with L. serricorne larvae, and the results suggested that activity is not restricted to isolates related to the Coleoptera-specific group. The results of our survey indicate that B. thuringiensis is part of the natural microflora in the stored-tobacco environment and that this special habitat represents a source of B. thuringiensis isolates that may be used to control stored-product pests.