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Abstract

Bacillus thuringiensis is an aerobic, spore-forming, gram-positive soil bacterium. This microorganism produces at the sporulation stage of its growth an intracellular crystal composed of one or more ���´-endotoxins. BLB459 is a new B. thuringiensis isolated in the laboratory of biopesticides from a Tunisian soil sample. In the present study, we focused on the screening of B. thuringiensis collection of 200 strains isolated from different variety of Tunisian soils and the characterization, using RFLP and molecular hybridization, of B. thuringiensis strain BLB459 having a distinctive plasmid profile. SmaI-PFGE typing confirmed the uniqueness of the DNA pattern of this strain, compared with BUPM95 and HD1 reference strains. PCR and sequencing assays revealed that BLB459 harbored three cry genes (cry30, cry40 and cry54) corresponding to the obtained molecular sizes in the protein pattern. Interestingly, PCR-RFLP assay demonstrated the originality of the BLB459 cry30-type gene compared to the other published cry30 genes. Insecticidal bioassays showed that BLB459 spore-crystal suspension was highly toxic to lepidopteran comparing with that of the commercial strain HD1 used as reference. Important histopathological effects of ���´-endotoxins on the tested larvae midgut were detected, traduced by the vacuolization of the apical cells, the damage of microvilli, and the disruption of epithelial cells. Such results indicated the interest of the new selected B. thuringiensis strain BLB459 and their cry toxins in the biological control of different lepidopteran insects such as lepidopteran and the possibility of its use for the formulation of new bioinsecticides.

Biography

Email: hanen.boukadi@gmail.com