Hyper-production of insecticidal crystal protein (delta-endotoxin) by Bacillus thuringiensis var. israelensis is not related to sporulation-specific biochemical functions

Hypertoxic mutant strains of Bacillus thuringiensis var, israelensis were i solated by mutagenesis of the parent strain. The correlation, if any, betwe en hyper-production of insecticidal crystal protein (delta-endotoxin) by hy pertoxic mutant strains of Bacillus thuringiensis var. israelensis and spor ulation-specific biochemical functions was studied. No increase in sporulat ion-specific biochemical markers was observed in the hypertoxic mutant stra ins. Asporogenous mutants of hypertoxic mutant strains blocked at different stages of sporulation were isolated, and larvicidal activity was studied. The hypertoxic parent strains and the sporulation-deficient, hypertoxic mut ant strains showed almost identical larvicidal activity. Therefore, the inc reased production of toxin is not related to sporulation-specific biochemic al changes.