New native Bacillus thuringiensis strains induce high insecticidal action against mosquito larvae and adults

Abstract

Abstract Mosquitoes of many species are key vectors in disease transmission, causing millions of fatalities worldwide each year. Insecticidal formulations based on Bacillus thuringiensis have been considered one of the most effective, ecologically safe, and long-lasting methods of managing insect pests. We established the isolation, identification, genetic characterization, and biological function of novel B. thuringiensis strains with strong control efficacy on mosquitoes. A collection of eight B. thuringiensis strains was isolated and identified as containing genes encoding typical endotoxins. Under light and scanning electron microscope, typical crystal forms of various shapes were observed in the B. thuringiensis strains. A total of fourteen cry and cyt genes were identified in the strains analyzed. While the B. thuringiensis A4 strain had twelve cry and cyt genes in the genome, not all the genes were expressed, and only a few protein profiles were detected. The eight B. thuringiensis strains showed larvicidal activity (LC50 range: 1.4–28.5 µg/ml and LC95 range: 15.3-130.3 µg/ml). Interestingly, the B. thuringiensis A4 strain showed a high level of toxicity to mosquito larvae and adults, as detected by bioassays under controlled conditions. These new findings show that the novel B. thuringiensis A4 strain could be used as a favorable candidate source to control larvae and adult mosquitoes in a sustainable manner that is friendly to the environment.