Genes chi of Native Bacillus thuringiensis Strains from Maranhão Active against Aedes aegypti Larvae

Bacillus thuringiensis is visualized as a multifaceted microbial factory for the production of several biomolecules. The Cry and Cyt proteins are used in commercial products sold worldwide as the most important bioinsecticides. However, there is increasing interest in lesser-known metabolites synthesized by B. thuringiensis, including Chi (chitinases) proteins. Several studies have observed that Chi proteins increase the insecticidal activity of Cry proteins, as these proteins degrade the peritrophic membrane, which is mainly composed of a chitin structure and proteins like those of Aedes aegypti larvae, allowing greater access of Cry proteins to their respective receptors on midgut cells. This research carried out a survey of strains of B. thuringiensis that amplified to the chi gene in combination with the cry and cyt genes and were pathogenic to Ae. aegypti larvae. The genomic DNA of 322 B. thuringiensis from different regions of the Maranhão, isolated from soil and water samples, were screened by PCR with primer pairs specific for the endogenous chitinase gene and 28 B. thuringiensis isolates were amplified, 14 of which were isolated from soil (published data) and 14 from water. Seven isolates killed 100% of the larvae within 24 hours and ten amplified for all the dipteran-specific cry and cyt genes. Ten isolates may be potential candidates to expand the alternative means in which these bacteria can be produced industrially as a biopesticide for the control of Ae. aegypti due to its high pathogenicity rate and great variability of the cry and cyt genes. However, more studies are needed for specific biotechnological applications and to potentially help in vector control, including determining the levels of chitinase synthesis in qualitative and quantitative assays to select B. thuringiensis isolates with a high level of protein production that could be a useful component of B. thuringiensis based biopesticides.