T7 phage factor required for managing RpoS in Escherichia coli

Significance Viruses that infect bacteria (phages) represent the most abundant living entities on the planet, and many aspects of our fundamental knowledge of phage–bacteria relationships have been derived in the context of exponentially growing bacteria. In the case of the prototypical Escherichia coli phage T7, specific inhibition of the housekeeping form of the RNA polymerase (Eσ 70 ) by a T7 protein, called Gp2, is essential for the development of viral progeny. We now reveal that T7 uses a second specific inhibitor that selectively inhibits the stationary phase RNA polymerase (Eσ S ), which enables T7 to develop well in exponentially growing and stationary phase bacteria. The results have broad implications for our understanding of phage–bacteria relationships and the therapeutic application of phages.