Induces the synthesis of acid phosphatase (AppA) and several other polypeptides (such as AppBC) during the deceleration phase of growth. It also acts as a transcriptional repressor for one group of proteins that are synthesized preferentially in exponential growth and for one group synthesized only in the stationary phase. Also involved in the stabilization of the sigma stress factor RpoS during stress conditions. Encoded by the cryptic lambdoid prophage DLP12.