Escherichia coli starvation diets: essential nutrients weigh in distinctly.

Bacterial growth is often limited by availability of nutrients. Soil, water, and even host environments such as macrophages can be nutrient poor, lacking essential building blocks for growth, including carbon, nitrogen, and phosphorus. The ratios of these elements differ according to the local ecology, so each one of them is limiting in different environments (4, 28). When presented with any type of starvation, Escherichia coli passes into a dormant mode, known as stationary phase, which protects the cells against harsh conditions. The master regulator of this response is RpoS. This review summarizes how cells sense starvation for carbon (glucose), phosphorus (inorganic phosphate), and nitrogen (ammonia) and subsequently turn on RpoS to initiate stationary phase. It was commonly thought that a universal signal, such as a general reduction in growth or slowing of macromolecule synthesis, communicated all types of starvation (16, 19). Surprisingly, each type of starvation triggers the pathway to stationary phase in a distinct fashion. Insights into the nature of the various starvation signals have been obtained by comparing different starvation conditions.