Activation and germination of spores of Bacillus thuringiensis var israelensis by alkaline pH and larval (Aedes aegypti) gut fluid.

Alkaline activation of the spores of crystalliferous (Cry+) and acrystalliferous (Cry-) strains of Bacillus thuringiensis var israelensis; wild type B. cereus and its transcipient crystalliferous derivatives and wild type B. subtilis was studied. Also the effect of larval (Aedes aegypti) gut fluid on the activation of spores of these strains was studied. Only the spores of the crystal forming strains were found to be activated by 0.1 M K2CO3 (pH 10) and by the larval gut fluid. The process of alkaline activation was independent of whether crystals were present with the spores in the activation solution. This indicates that protoxin in the spore coat is responsible for the alkaline activation process and may have ecological implications for the organism.