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. Interacts with RsbRA and RsbS in the stressosome. The stressosome probably also contains RsbRC and RsbRD. Phosphorylated by RsbT. Cells lacking this gene have an increased sigma-B activity in response to salt and ethanol stress and also increased sigma-B activity in response to the energy stress associated with entry into stationary phase. These results indicate that this protein is a negative regulator of sigma-B activity.