CONTRIBUTION OF THE INDIVIDUAL COMPONENTS OF THE DELTA-ENDOTOXIN CRYSTAL TO THE MOSQUITOCIDAL ACTIVITY OF BACILLUS-THURINGIENSIS SUBSP ISRAELENSIS

The delta-endotoxin crystal of the mosquitocidal bacterium Bacillus th uringiensis subsp. israelensis contains four major delta-endotoxins. E xpression systems were devised to synthesize each of the four toxins a t concentrations at which they formed inclusion bodies in an acrystall iferous mutant of Bacillus thuringiensis. The relative activities of t hese inclusions were then determined against Aedes aegypti larvae. Bio assays of mixtures of the individual toxins revealed a number of syner gistic interactions which explained in part why the native crystal is considerably more toxic than any of the individual toxins.