Sigma factors are initiation factors that promote the attachment of RNA polymerase (RNAP) to specific initiation sites and are then released. This sigma factor is involved in the transition to post-exponential phase in the beginning of sporulation. It is also required for transcription of several stationary phase genes. Association with the RNAP core increases rapidly in early exponential phase, and reamins constant expression level after (PubMed:21710567). Interacts transiently with the RNAP core. Association with RNAP core increases during sporulation but not tested stresses (at protein level). Belongs to the sigma-70 factor family.