Distribution and diversity of cry genes in native strains of Bacillus thuringiensis obtained from different ecosystems from Colombia

Colombia is a tropical country located at the north of South America. It is considered to be one of the most important countries in terms of its biodiversity worldwide. One hundred and eight soil samples obtained from agricultural crops and wild ecosystems were evaluated in terms of the presence of Bacillus thuringiensis (Bt) native strains. One hundred and eight different Bt strains were isolated and characterized by the presence of crystal proteins by SDS-PAGE and a multiplex PCR with general and specific primers for cry1 and cry3, cry7, and cry8 gene detection. Most of the Bt strains (73%) reacted with the cry1 general primers; 27.8% of the Bt strains reacted with cry3, cry7, and cry8 general primers and 17.8% of strains did not react with any of these two sets of primers. Thirty different PCR profiles were found in the strains with cry1 genes when they were analyzed with specific primers (cry1A to cry1F). A high frequency of joint occurrence was observed for cry1Aa/cry1Ab, cry1Aa/cry1Ac, cry1Ab/cry1Ac, and cry1C/cry1D genes with a Pearson coefficient of 0.88, 0.74, 0.76, and 0.87, respectively. Other distinctive characteristics were found in the Colombian collection as the presence of 22.2% of native strains which presented, at the same time, lepidopteran and coleopteran active genes. Interesting relations were found as well between the cry gene distribution and the geographical areas sampled. Finally, some strains with moderate to high biopesticide activity against Spodoptera frugiperda (Lepidoptera) and Premnotrypes vorax (Coleoptera) insects were identified, this being important to explore future microbial strategies for the control of these crop pests in the region.