Sigma B Contributes to PrfA-Mediated Virulence inListeria monocytogenes

Transcription of the Listeria monocytogenes positive regulatory factor A protein (PrfA) is initiated from either of two promoters immediately upstream of prfA (prfAp(1) and prfAp(2)) or from the upstream plcA promoter. We demonstrate that prfAp(2) is a functional sigma(B)-dependent promoter and that a sigB deletion mutation affects the virulence phenotype of L. monocytogenes. Thus, the alternative sigma factor sigma(B) contributes to virulence in L. monocytogenes.