Abstract
Studies of bacterial diversity and richness of the soil are keys for developing effective bio pesticides for the bio control against plant pests and Diptera vectors of diseases (malaria, dengue ...). In this manuscript, the characterization of the bacterial diversity of broadleaf and needle Lebanese soils was studied compared to the same soils in Austria, a different geographical area and under different climate. Classes and genera compositions of the Firmicutes phylum and its abundance in the different soils studied were particularly characterized using diversity indices (alpha, beta, OTUs…) and molecular methods (SSCP and qRT-PCR). From the broadleaf and needle Lebanese soils and precisely from this phylum, strains of Bacillus thuringiensis were screened for their insecticidal activity against dipteran larvae, Culex pipiens, Aedes albopictus and Anopheles gambiae. Two Bt strains were selected. A23 strain has toxicity in vivo higher than the reference strain Bacillus thuringiensis isarelensis (Bti). However, this strain didn’t reveal any genetic and molecular differences from Bti. The H3 strain, meanwhile, was being investigated for being non-cytolytic and having an insecticidal activity in vivo against Diptera but at high concentrations compared to Bti. This strain showed a different gene and protein content compared to Bti. H3 probably has a new variant of cry4B gene and a new variant of cry40 gene known to have an insecticidal activity. Additional investigations are needed to confirm these results and to understand the mechanisms of toxicity of these two strains.