Pleiotropic control of Listeria monocytogenes virulence factors by a gene that is autoregulated

Abstract

Summary: Evidence for ptelotropic activation of virulence genes in Listeria monocytogenes is presented. A complementation study of a spontaneous prfA‐deletion mutant and analysis of cassette and transposon insertion mutants showed that the gene prfA activates the transcription of four independent genes which code for a phosphatidyl‐inositol‐specific phospholipase C (gene plcA), listeriolysin O (gene hlyA), a metallo‐protease (gene prtA) and a lecithinase (gene prtC). Transcription of prfA is not constitutive. During the growth phase, two peaks of prfA transcript accumulation were observed: the first was during exponential growth, and the second was at the beginning of the stationary phase. In addition, two prf4‐specific transcripts of 2.2 kb and 1 kb are detected. Early in exponential growth, prfA is co‐transcribed with plcA which lies upstream prfA, giving rise to the 2.2 kb plcA‐prfA transcript. In late‐exponential growth and at the beginning of the stationary phase, prfA transcripts of 1 kb are predominantly detected. Our results demonstrate that since prfA controls plcA transcription, it also regulates its own synthesis.