Inhibitor of Spx proteolytic control. Acts by interacting with SpxH/YjbH, which disrups interaction between SpxH and Spx, and inhibits SpxH-enhanced proteolysis of Spx by ClpXP (PubMed:21378193). Required for the stabilization of Spx and activation of Spx-regulated genes in response to cell wall stress (PubMed:30001325). Interacts with SpxH. Induced under cell wall stress, but not disulfide stress, and this induction requires the CssRS two-component system, which responds to both secretion stress and cell wall antibiotics. Phosphorylated CssR acts as an anti-repressor by antagonizing YuxN repression. Deletion of the gene causes a decrease in the overall Spx levels, as well as a change in the dynamics of Spx accumulation.