Stress and the single cell: intrapopulation diversity is a mechanism to ensure survival upon exposure to stress.

We traditionally celebrate the capacity of bacteria for growth in a diverse range of environmental niches. As the attention has switched to their survival, we are no less impressed by the diversity of mechanisms that aid survival upon exposure to a variety of stresses. Mechanistically, we usually measure adaptation by the changes that occur upon rapid transfer from condition A to B. Implicit in such analyses is the homogeneity of the population of cells in terms of their biochemistry and responsiveness. In contrast, the literature contains many reports of heterogeneity within bacterial populations. A practical importance of such heterogeneity is the ability of a small fraction of any population to survive exposure to stresses that kill the majority of the population. The origins and properties of such organisms have been receiving renewed attention. This brief review considers some of the routes by which heterogeneity is generated in bacterial populations and suggests that such inherent transient diversity in phenotype of individual cells is a survival aid.