Biodiversity of Qatari Bacillusthuringiensisstrains and molecular prediction of their biological activities and bioassays: for a safer and clean environment

Abstract

Abstract Qatar's soil and environment are sources of beneficial bacterial strains and bacterial resources that should be first of all, identified, isolated, studied, used and valorized. In fact, the Qatari environment should be elective for many microbial genetic resources tolerant to high temperature, drought, salinity and hydrocarbon rich soil. Isolating microbial strains having biotechnological applications would be very beneficial not only for Qatar, but also for the Gulf region and other countries in the world. B. thuringiensis is a Gram-positive bacterium which produces, during sporulation, crystalline inclusions containing one or more deltaendotoxins, that are considered as the best biological insecticides as they are harmless for man and animal and act specifically against a wide variety of pathogenic insects, including pests and disease vectors. In this research project, we studied 31 crystal producing Qatari B. thuringiensis isolates, by the investigation of their plasmid patterns, crystal morphology, deltaendotoxin identification by SDS-PAGE, prediction of gene nature by PCR and insecticidal activities. The crystal morphology comparison showed that 22.5 % were spherical, 32.2 % were amorphous, 38.7 % were pyramidal and 6.4 % were bipyramidal. Based on the isolates plasmid patterns, 11 representative strains of the different classes were deeply studied. We used their molecular ribotyping and bioinformatic tools of sequence and BLAST alignment, to confirm that the studied isolates are B. thuringiensis strains. By SDS-PAGE, we showed that the deltaendotoxins produced by the different strains have different molecular weights. The PCR screening of these strains, using oligonucleotides specific for the genes cry1 and cry4, showed the presence of genes cry1A in two strains and allowed us to predict their potential insecticidal activities against lepidopteran larvae. Moreover, we used a B. thuringiensis israelensis in bioassay experiments against local mosquito Culex pipiens larveae and demonstrated the efficacy of such biological bioinsecticides on Qatari mosquitoes. These results are very encouraging and favour the use of B. thuringiensis local strain bioinsecticides for environmentally safe integrated pest management in this region.