| Salmonella are able to respond to carbon starvation by undergoing genetic and physiologic changes, known as the starvation-stress response (SSR). These changes help the cell fight the effects of long term C-starvation and generate increased resistance to a variety of other environmental stresses (i.e., C-starvation-inducible or CSI cross-resistance). SixA is a phosphohistidine phosphatase implicated in the inhibition of the His-to-Asp phosphorelay between ArcB and ArcA, and appears to play a role in down-regulating expression of the ArcAB modulon by reducing the amount of phosphorylated ArcA. We hypothesized, the response regulators of two component systems, BaeSR, PmrAB, PhoPQ, PhoBR, and phosphorelay system ArcAB play roles in the development of the SSR of Salmonella enterica serovar Typhimurium and could be possible targets for SixA regulation. We developed a working model in which under aerobic carbon-starvation conditions ArcB kinase activity is greatly increased and ArcB can cross-phosphorylate at least one other response regulator. Of the systems studied we suggest the response regulators PhoP, PmrA, and PhoB as the most likely targets of ArcB kinase activity during carbon starvation. |
