Molecular and functional characterization of a highly mosquitocidal Bacillus thuringiensis strain VCRC-B669

Mosquito-borne diseases (MBDs) continue to pose a significant public health burden, and controlling mosquito populations remains a key strategy for reducing disease transmission. Extensive use of chemical insecticides causes environmental issues and leads to the development of resistance in mosquito populations. Entomopathogenic bacteria are increasingly being explored as environmentally safe alternatives for mosquito control. In the present study, a mosquitocidal bacterial strain was characterized and evaluated for its larvicidal potential against medically important mosquito vectors. The mosquitocidal bacterial isolate was identified using MALDI-TOF MS, 16 S rRNA gene sequencing, housekeeping genes, and detection of Bacillus thuringiensis ( Bt) crystal-insecticidal protein genes, viz., cry4A , cry4B , cry10 , cry11 , and cyt1 , cyt2 . Growth dynamics and protein production were monitored over a 96-h cultivation period. Larvicidal efficacy was evaluated against late third-instar larvae of Aedes aegypti , Anopheles stephensi , and Culex quinquefasciatus . SDS-PAGE was used to examine insecticidal crystal proteins, whereas conserved toxin domains in Cry4A and Cyt2 were analyzed using InterProScan. The isolate was identified as Bt strain VCRC-B669 and exhibited potent larvicidal activity, with LC₅₀ values of 0.0014, 0.0036, and 0.0070 µg/mL against Ae. aegypti , An. stephensi , and Cx. quinquefasciatus , respectively. SDS-PAGE consistently revealed major protein bands at approximately 130, 70, and 27–30 kDa, InterProScan analysis identified conserved protein domains and sequence features within the translated Cry4A and Cyt2 sequences. These findings indicate that B. thuringiensis VCRC-B669 has considerable potential for development as a microbial larvicide for integrated mosquito vector management.