An organism's survival from moment to moment depends, at least in part, on its ability to sense and respond to changes in its environment. Mechanisms for responding to environmental changes are universally present in living beings. For example, when mammals perceive a sudden environmental change as threatening, a rush of adrenaline precipitates the well-known “fight or flight” response. Such physiological stress responses in complex organisms require appropriately regulated interactions among numerous organ systems. But how do single-celled organisms respond to potentially lethal threats? The hope is that identifying specific mechanisms that contribute to microbial survival under rapidly changing conditions will provide insight into stress response systems across life forms.