CORRELATION BETWEEN ALKALINE ACTIVATION OF BACILLUS-THURINGIENSIS VAR, KURSTAKI SPORES AND CRYSTAL PRODUCTION

The spores of crystal-forming (Cry(+)) and non-crystal-forming (Cry(-) ) strains of Bacillus thuringiensis var. kurstaki and Bacillus cereus were tested for the ability to be activated by 0.1 M K2CO3 (pH 10). On ly the spores of crystal-forming strains could be activated, and this phenotype was independent of whether crystals were present with the sp ores in the activation solution, The spores of a B. thuringiensis var. kurstaki strain that is temperature sensitive for protoxin accumulati on could be activated by the alkaline solution when produced at the pe rmissive temperature, whereas spores produced at the nonpermissive tem perature were not activated. The results indicate that protoxin in the spore coat is responsible for the alkaline-activation phenotype and m ay serve an ecological function for the organism.