Bioprospecção de bactérias entomopatogênicas do Sudeste do Piauí com ação larvicida para Aedes aegypti

Abstract

Aedes aegypti is currently a major public health problem, being responsible for the spread of infectious diseases that have been causing epidemics worldwide. In this context, the biological control of this vector is an efficient and more sustainable alternative compared to chemical routes, and presents some environmental advantages, such as biodegradability and low or no toxicity to the environment. Bioinsecticides based on Bacillus thuringiensis (Bt) have shown satisfactory results in the control of Diptera, due to the production of proteins called Cry and Cyt. Therefore, this study aimed to isolate, characterize and test the activity of Bt bacteria from soils in the state of Piauí on Aedes aegypti larvae. The isolates were obtained from soil samples from nine municipalities in southeast Piauí, and the characterization and identification of B. thuringiensis colonies was based on morphological characteristics. Bioassays were performed to evaluate the pathogenicity and toxicity of the different strains of B. thuringiensis against third-instar larvae of A. aegypti. The soil samples from the 9 municipalities in the region subjected to bacterial isolation generated 421 bacterial colonies with macroscopic morphology typical of Bt. Of the total samples, 13% of the colonies presented microscopic morphology similar to Bt and only the strain, originating from the soil of Ribeira do Piauí, was positive against the Aedes aegypti larvae, with 100% of the larvae dead within 32 minutes, with a Lethal Concentration of 0.035 mL. Therefore, Bacillus thuringiensis is a viable alternative, with biotechnological potential, for controlling vectors of diseases of importance to public health. However, further studies and new experiments are important, including genetic sequencing to analyze the gene responsible for the production of the Cry protein.