Isolation of Bacillus thuringiensis serovar israelensis VCRC-B650 from Indian clay soil with enhanced mosquitocidal activity and dehairing property

The use of microbial agents is an environmentally friendly approach to mosquito control, wherein natural enemies of mosquitoes are employed to control mosquito populations. A novel mosquitocidal bacterium was isolated from clay soil from the Union Territory of Puducherry, India, and was identified as Bacillus thuringiensis serovar israelensis (Bti), de Barjac (VCRC-B650) (Bacillales: Bacillaceae) through whole genome sequencing (WGS), along with the amplification of cry (cry4A, cry4B, cry10, cry11), and cyt (cyt1, cyt2) genes. Bioassays conducted against mosquito larvae (Diptera: Culicidae) demonstrated varying degrees of susceptibility to Bti VCRC-B650, with the larvae of the dengue vector, Aedes aegypti (Linnaeus), exhibiting the highest susceptibility (LC₅₀ = 0.0049 and LC₉₀ = 0.0084 mg l⁻¹). The filarial vector, Culex quinquefasciatus (Say), showed moderate susceptibility (LC₅₀ = 0.0054 and LC₉₀ = 0.0094 mg l⁻¹), while the malarial vector, Anopheles stephensi (Liston), displayed the lowest susceptibility (LC₅₀ = 0.0104 and LC₉₀ = 0.0215 mg l⁻¹). Compared to the WHO standard strain Bti H-14, the Bti VCRC-B650 isolate was observed to be more efficient and has not exhibited adverse effects on non-target aquatic organisms. This study revealed that the new strain of Bti (VCRC-B650), can be employed in vector control with dual functions such as mosquitocidal activity and the ability to produce protease with dehairing property.