[Stationary phase in Escherichia coli]

When nutrients become scarce E. coli cells enter into a non-growth phase known as stationary and develop a multiple-stress resistance state analogue to sporulation in B. subtilis. Morphological changes are observed, including rounded shape, loss of flagella and thickening of the cell wall. General metabolism is redirected, macromolecular degradation is increased, and storage and osmoprotection compounds are synthesized. The reorganization of the nucleoid is accompanied by an overall repression of gene expression, but a subset of genes required for starvation survival become transcribed in a manner dependent on the stationary phase-specific subunit of RNA polymerase (RpoS or sigma(s)). The regulatory function of sigma(s) seems to be central to a global gene network that is beginning to be understood. Also, stationary phase populations are highly heterogeneous in properties as viability, genotype, and mutability. The emergence of mutant subpopullations capable of using nutrient traces suggest survival strategies during long term starvation. This review focuses on the major characteristics of E. coli during stationary phase and on the regulatory gene network responsible of such characteristics.