Isolation and characterisation of Bacillus velezensis WHk23 as a potential mosquitocide

Mosquitoes transfer several diseases to humans and animals in many parts of the world. Mosquito control depends mainly on chemical insecticides which can lead to insecticide resistance, environmental problems and health issues. In this paper, we report the isolation and characterisation of a potential mosquitocidal bacterial strain (Bacillus velezensis WHk23) belonging to the operational group Bacillus amyloliquefaciens. Phylogenetic analysis using rpoB gene confirmed that the isolate belongs to Bacillus velezensis. Genetic analysis by polymerase chain reaction indicated the presence of genes encoding for several lipopolypeptides and polyketides such as surfactin, bacillomycin, fengycin, iturin, macrolactin, bacillaene and difficidin. Crude toxin from the bacterial strain demonstrated larvicidal and pupicidal activity against both Anopheles stephensi and Culex quinquefasciatus. Larval LC50 was 25.41 and 33.97 µg/ml while pupal LC50 was 4.05 and 12.63 µg/ml for An. stephensi and C. quinquefasciatus, respectively. With increasing reports of mosquito resistance to different chemical and biological insecticides, these results suggest that the new isolate may have a potential for use as a safe environmentally friendly alternative for mosquito control.