Contribution of the individual components of the d-endotoxin crystal to the mosquitocidal activity of Bacillus thuringiensis subsp. israelensis

The delta-endotoxin crystal of the mosquitocidal bacterium Bacillus thuringiensis subsp. israelensis contains four major delta-endotoxins. Expression systems were devised to synthesize each of the four toxins at concentrations at which they formed inclusion bodies in an acrystalliferous mutant of Bacillus thuringiensis. The relative activities of these inclusions were then determined against Aedes aegypti larvae. Bioassays of mixtures of the individual toxins revealed a number of synergistic interactions which explained in part why the native crystal is considerably more toxic than any of the individual toxins.