Negatively regulates RNA polymerase sigma factor SigO-dependent transcription. Prevents the expression or secretion of OxdC under nonstress conditions. May act as an anti-sigma factor. Preferentially expressed in cells competent for DNA transformation; that is 5-15% of the population (PubMed:11918817). Expression activated by ComK (PubMed:11918817). Positively regulated by SigO and its coactivator RsoA. Cells lacking this gene exhibit a slight increase in OxdC accumulation under acidic growth conditions and a huge increase under nonstress growth conditions.