Exploring Bacillus thuringiensis from soil as a potential biocontrol strategy for mosquito larvae

Abstract

The global burden of mosquito-borne diseases, including dengue, Zika, and chikungunya, has escalated the need for sustainable vector control strategies. The mosquito Aedes aegypti, the primary vector of these diseases, poses significant public health challenges due to its adaptability and increasing resistance to chemical insecticides. This study explores the potential of Bacillus thuringiensis (Bt), a soil-dwelling bacterium, as a biocontrol agent against mosquito larvae including Aedes aegypti. Soil samples from diverse ecological regions were screened for native Bt strains, followed by their isolation and characterization. Soil suspensions (1 % w/v) were heat treated and cultured on nutrient agar medium and incubated aerobically at 37 °C for 24 and 48 h. Around 166 colonies isolated were identified by Gram staining and endospore stains. Fifteen isolates were identified as B. thuringiensis depending on their crystal protein formation, morphologically, and biochemically test results. Bacterial cell suspension with and without culture supernatant were used to carry out bioassays against the larvae of mosquitoes at 48 and 96 h. Isolate numbers A21, S1, BT1 and BT5 have shown 100 % of mortality and isolates A29, S9, N23 and BT2 have shown above 50 % of toxic activity in bioassay procedures. Isolate N5 has not shown any significant larvicidal activity. Hence, molecular identification of these isolated strains needs to be done in the near future. Our findings underscore the efficacy of indigenous Bt strains as a viable and environmentally friendly alternative to chemical insecticides. By leveraging locally adapted microbial resources, this study contributes to the development of sustainable biocontrol strategies tailored to regional needs. The results hold promise for reducing the public health burden of mosquito-borne diseases, particularly in tropical and subtropical regions where mosquito-borne diseases are endemic.