Identification and characterization of a relA-dependent starvation-inducible locus (sin) in Salmonella typhimurium.

By use of Mu cts d1(Ap lac) phage, a strain of Salmonella typhimurium was isolated containing a Mu d insertion in a locus (sinA) which is induced during nicotinate, thiamine, purine, amino acid, phosphate, and carbon starvation conditions. Depending on the starvation condition, a 2- to 10-fold increase in beta-galactosidase activity was demonstrated. The sinA locus, which mapped at 32 U, became induced after a decline in growth rate due to starvation. The introduction of relA into the sinA-lac strain prevented induction by nicotinate starvation and partially prevented induction by phosphate starvation. The data suggest that sinA responds to changes in growth rate due to various nutrient starvation conditions and probably responds in part to changes in guanosine tetraphosphate levels.