The role of homoserine lactone in the activation of Escherichia coli stationary phase genes

Abstract

The rpoS protein, $\rm\sigma\sp{s},$ is responsible for regulating the expression of a wide array of proteins. Believed to induce $\rm\sigma\sp{s},$ homoserine lactone (HSL), a threonine pathway derivative, has been implicated in the control the rpoS gene system. The $\rm\sigma\sp{s}$ protein regulates the expression of many genes needed for survival during starvation. At the starvation-triggered onset of stationary phase in Escherichia coli, an increase in the transcription of rpoS is exhibited. By using both batch and continuous cultures, the role of HSL in the activation of the rpoS regulon was investigated in both complex and minimal media. Complex media provided no additional information on the impact of HSL on the reporter protein levels. However, using minimal media in batch cultures, HSL increased the levels of the reporter protein and was not cell density dependent.