Bacterial suicide through stress

Outside of the laboratory, bacterial cells are constantly exposed to stress ful conditions, and an ability to resist those stresses is essential to the ir survival. However, the degree of stress required to bring about cell dea th varies with growth phase, amongst other parameters. Exponential phase ce lls are significantly more sensitive to stress than stationary phase ones, and a novel hypothesis has recently been advanced to explain this differenc e in sensitivity, the suicide response. Essentially, the suicide response p redicts that rapidly growing and respiring bacterial cells will suffer grow th arrest when subjected to relatively mild stresses? but their metabolism will continue: a burst of free-radical production results from this uncoupl ing of growth from metabolism, and it is this free-radical burst that is le thal to the cells, rather than the stress per se. The suicide response hypo thesis unifies a variety of previously unrelated empirical observations, fo r instance induction of superoxide dismutase by heat shock, alkyl-hydropero xide reductase by osmotic shock and catalase by ethanol shock. The suicide response also has major implications for current [food] processing methods.