Adaptive responses to oxygen limitation in Escherichia coli.

Escherichia coli can grow under either aerobic or anaerobic conditions, deriving energy from a variety of respiratory of fermentative processes. The switch between different metabolic modes depends on the availability of oxygen or alternative electron acceptors, and it is controlled by regulatory mechanisms which ensure that the most energetically favourable metabolic mode is adopted in a specific environment. This article reviews the properties of two transcriptional regulators, ArcA and FNR, which control the expression of networks of genes in response to oxygen limitation.