Journal of Applied Microbiology, Vol.119, No.6, 1692-1699, 2015
Bacillus thuringiensis subsp israelensis producing endochitinase ChiA74 triangle sp inclusions and its improved activity against Aedes aegypti
Aims: The objective of this study was to produce stable inclusions of chitinase ChiA74Dsp in Bacillus thuringiensis subsp. israelensis ( Bti) and to assay its insecticidal activity against Aedes aegypti larvae. Methods and Results: Bti was transformed with chiA74 triangle sp regulated by its own promoter or by the strong chimeric cytAp/STAB-SD promoter system to generate two recombinant Bti strains. These recombinants produced their native parasporal bodies composed of Cry4Aa, Cry4Ba, Cry11Aa and Cyt1Aa and ChiA74Dsp inclusions, and showed a approx. threefold increase in both endochitinase activity and viable spore count when compared with the parental strain. Both recombinants were approximately twofold more toxic (LC50s 8.02, 9.6 ng ml(-1)) than parental Bti (19.8 ng ml(-1)) against 4(th) instars of A. aegypti larvae. Conclusions: ChiA74Dsp inclusions, together with the insecticidal crystals and spores of Bti increased the toxicity against A. aegypti larvae by at least twofold. Significance and Impact of the Study: We report for the first time the engineering of Bti to produce spore-parasporal body-ChiA74 triangle sp inclusions in the same sporangium, which are released together following autolysis. Our work lays a foundation for engineering Bti to produce more efficacious combinations of Cry4Aa, Cry4Ba, Cry11Aa, Cyt1Aa and chitinase inclusions.