[Viability of Bacillus subtilis auxotrophs in the absence of their essential metabolites]

The effect of tryptophan and uracil starvation on the viability of the transformant B. subtilis BSA 170 trp- ura- and its parent strains Bacillus subtilis PB 168 trp -C and Bacillus subtilis PB 3308 ura- was examined. These studies were performed at the conditions for competence development, during 16 hours. Our results showed that B. subtilis BSA 170 was resistant to tryptophan-less death during all the assay and was also resistant to uracil-less death during three hours. After this time, viability measurements revealed less colony forming units per milliliter, and decrease of the culture absorbances. The uracil-less death required the presence of tryptophan suggesting that protein synthesis is needed. The parental strains exhibit similar behavior. Bacillus subtilis PB 168 was resistant to tryptophan-less death and B. subtilis PB 3308 showed decrease of the viability after uracil starvation comparable to that of the transformant strain.