Characterization of a new highly mosquitocidal isolate of Bacillus thuringiensis - an alternative to Bti?

The mosquito is a very important vector involved in the worldwide transmission of disease-causing viruses and parasites. Controlling the mosquito population remains one of the best means for preventing the serious infectious diseases of malaria, yellow fever, dengue, filariasis and so on and there has been an increasing interest in developing biopesticides as a useful substitute to chemical insecticides. As a result, Bacillus thuringiensis subsp. israelensis (Bti) has been extensively used due to its specificity and high toxicity to a variety of mosquito larvae. However it is prudent to seek alternatives to Bti with alternative spectra of mosquitocidal activity or that are able to overcome any resistance that might develop against Bti. The Bt S2160-1 strain was isolated from soil samples collected from Southern China and found to have a comparable mosquitocidal activity to Bti. However there were significant differences in terms of their plasmid profiles, crystal proteins produced and cry gene complement. A PCR-restriction fragment length polymorphism identification system was developed and used in order to identify novel cry-type genes and four such genes (cry30Ea, cry30Ga, cry50Ba and cry54Ba) were identified in Bt S2160-1. In conclusion, Bt S2160-1 has been identified as a potential alternative to Bti, which could be used for the control of mosquito populations in order to reduce the incidence of mosquito-borne diseases.