[On the adaptive nature of the dissociation process in Bacillus thuringiensis]

The process of dissociation into variants differing in colony morphology occurring in batch cloned cultures of two Bacillus thuringiensis strains belonging to different subspecies was studied at optimal and elevated temperatures. An increase in the cultivation temperature to 40 degrees C resulted in an increase in the fraction of R variants to 100% after 72 h of cultivation of either of the strains. This increase was not due to the selection of forms with greater resistance to elevated temperature. The level of resistance to elevated temperature was determined by the strain genotype and did not correlate with morphological characteristics of the colonies.