Isolates of Bacillus thuringiensis from Maranhão biomes with potential insecticidal action against Aedes aegypti larvae (Diptera, Culicidae)

Abstract

Entomopathogenic agents are viable and effective options due to their selective action against insects but benign effects on humans and the environment. The most promising entomopathogens include subspecies of Bacillus thuringiensis (Bt), which are widely used for the biological control of insects, including mosquito vectors of human pathogens. The efficacy of B. thuringiensis toxicity has led to the search for new potentially toxic isolates in different regions of the world. Therefore, soil samples from the Amazon, Cerrado and Caatinga biomes of the state of Maranhão were evaluated for their potential larvicidal action against Aedes aegypti. The isolates with high toxicity to mosquito larvae, as detected by bioassays, were subjected to histological evaluation under a light microscope to identify the genes potentially responsible for the toxicity. Additionally, the toxic effects of these isolates on the intestinal epithelium were assessed. In the new B. thuringiensis isolates toxic to A. aegypti larvae, cry and cyt genes were amplified at different frequencies, with cry4, cyt1, cry32, cry10 and cry11 being the most frequent (33-55%) among those investigated. These genes encode specific proteins toxic to dipterans and may explain the severe morphological changes in the intestine of A. aegypti larvae caused by the toxins of the isolates.

Educação em saúde para o controle de Aedes aegypti

“…O controle vetorial de mosquitos de importância médica é realizado em diversas partes do mundo, através de inseticidas químicos sintéticos das classes dos temefós, organofosforados e piretróides e/ou por meio de fitoinseticidas e micro-organismos, especialmente as bactérias Bacillus thuringiensis israelenses (Bti) e Wolbachia, considerados os agentes biológicos mais específicos no controle de mosquitos, uma vez que não representam riscos para os seres humanos (AHMAD et al, 2021;VIANA et al, 2021).…”

Strain of Bacillus thuringiensis from Restinga, toxic to Aedes (Stegomyia) aegypti (Linnaeus) (Diptera, Culicidae)

“…The biological control is a sustainable alternative to reduce the vector population indexes (Huang et al, 2017). The Bacillus thuringiensis (Berliner, 1911) is an important insects' pathogen and exhibits high toxicity for diptera larvae (Campanini et al, 2012;Soares-da-Silva et al, 2017;Lobo et al, 2018;Zghal et al, 2018;Viana et al, 2020).…”

“…The B. thuringiensis produces protein crystals during the sporulation phase; these crystals are made of δ-endotoxins or Cry and Cyt proteins (Soberón et al, 2018), encoded by cry and cyt genes, located at conjugative plasmids (Berry et al, 2002). The proteins become toxic to the larvae after they ingest them, because in the larvae's medium intestine the proteins are solubilized, due to the alkaline pH, freeing protoxins that bind to specific receptors in the intestinal epithelium, causing the pore formation on the cellular membrane, which leads to a ionic imbalance and larval death (Soberón et al, 2018;Viana et al, 2020).…”

Larvicide Activity of Bacillus Thuringiensis Var. Israelensis. In Simulated Field Condition/ Atividade Larvicida De Bacillus Thuringiensis Var. Israelensis. Em Condição Simulada De Campo

“…Due to the resistance acquired by populations of the mosquito Ae. aegypti, alternatives for its control are widely studied, such as the use of biological agents [BATRA et al, 2000;LIMA et al, 2005;SOARES-DA-SILVA et al, 2017;VIANA et al, 2021).…”