A relA(S) suppressor mutant allele of Bacillus subtilis which maps to relA and responds only to carbon limitation.

The histidine analog 3-amino-1,2,4-triazole (AT) was used for the selection of spontaneous AT-resistant revertants of a relA mutant of Bacillus subtilis. One of these revertants, L3, showed a unique phenotype; it did not respond to amino acid starvation, like the relA mutant, but it did respond to glucose starvation by the accumulation of (p)ppGpp, unlike its parent. Genetic analysis revealed that this suppressor mutant (relA(S)) allele mapped to the relA locus at 239 degrees on the B. subtilis chromosome.