Crucial roles of MicA and RybB as vital factors for σ-dependent cell lysis in Escherichia coli long-term stationary phase.

σ(E)-dependent cell lysis has been proposed to eliminate damaged cells in the stationary phase in Escherichia coli. In order to explore the relationship of this process to long-term stationary phase existence, we considered that micA and rybB could be important small regulatory RNA (sRNA) genes for σ(E)-dependent cell lysis. A long-term stationary phase was observed at temperatures of <37°C, but not >38°C, and was found even in an rpoS knock-out background. Strains with disrupted micA or rybB were incapable of long-term stationary phase existence. Both strains drastically lost survivability accompanied by a dramatic accumulation of mutations. These findings allow us to speculate that σ(E)-dependent cell lysis plays a key role in the establishment of the long-term stationary phase, presumably by eliminating damaged cells and thus preventing the over-accumulation of mutations.