Potencial larvicida de bactérias isoladas de ambientes amazônicos para o controle de Aedes aegypti (Linnaeus, 1762)

Abstract

The Aedes aegypti mosquito is the main vector of the arboviruses that cause Dengue, Urban Yellow Fever, Zika and Chikungunya. One of the main tools used to control this vector is chemical insecticides, however, their continued use can cause negative effects on the environment and human health, as well as selecting resistant mosquitoes. In this sense, finding new alternatives for its control, such as biological control using entomopathogenic microorganisms, can be a promising biotechnological alternative in the control of disease vectors. Therefore, this study aims to evaluate the chemical and biological potential of Amazonian bacteria isolated from sediments for the control of Ae. aegypti under laboratory conditions. The samples were collected from three lakes in the municipality of Parintins, a peri-urban area of the municipality. The samples were then sent to the INPA Malaria and Dengue Laboratory, where the following procedures were performed: isolation in two culture media (NA and PDA), purification, Gram staining, and then preservation and storage of the bacteria. For the biological assays, 50 µL of the pre-inoculum added to 5 mL of the respective media was used. Larval mortality was assessed up to 72 hours after exposure to bacterial cultures. A total of 50 bacteria were isolated using NA (23) and PDA (27) media. Of the 50 bacteria, 2 active strains (P2LM3NA and P2LM5NA) for Aeaegypti larvae were identified by sequencing the 16s rRNA gene. The P2LM5NA strain was selected to obtain extracts and evaluate its larvicidal potential. The exposure of Ae. aegypti to the metabolic extract of the supernatant of the P2LM5NA strain revealed 100% mortality of L3 larvae within 24 hours at two concentrations tested. The extract obtained from the cellular component showed 70% activity after 72 hours of exposure at a concentration of 100 µL. Sequencing of the 16S rRNA gene and BLAST analysis allowed the identification of the bacterial strains of this study, where it was possible to observe that the bacterial strains active against Ae. aegypti present similarity of 99.88% (P2LM5NA) and 97% (P2LM3NA) with the genus Bacillus. Bacterial species that exhibit remarkable larvicidal activity were isolated compared to that of a commercial product Natular® DT. The bacterial strains with larvicidal potential isolated from three Amazonian lakes, obtained in this study, may be new entomopathogenic agents for the biological control of A. aegypti populations.