One of 4 functionally non-identical RsbR paralogs, it functions in the environmental signaling branch of the general stress response. Negative regulator of sigma-B activity. Non-phosphorylated RsbS binds to RsbT, preventing its association with RsbU. Requires any one of RsbRA, RsbRB, RsbRC or RsbRD to sequester RsbT. When RsbS and the RsbR paralog(s) are phosphorylated, they release RsbT, which can then bind and activate RsbU. Probably present in the stressosome with RsbRA, RsbRB, RsbRC and RsbS. Phosphorylated by RsbT. Cells lacking this gene have no visible phenotype is response to salt, ethanol or energy stress. However cells with multiple disruption (RsbRA, RsbRB and RsbRD) have an increased basal level of sigma-B, indicating this protein is a negative regulator of sigma-B.