The Listeria monocytogenes prf AP2 promoter by sigma B in a growth phase dependent is regulated manner

Listeria monocytogenes prfA, encoding positive regulatory factor A, is transcribed from three promoters (prfAP1, prfAP2, and PplcA). The prfAP2 promoter was previously proposed to be sigma B (sigma(B))-dependent. This hypothesis was tested by creating prfA promoter-gus transcriptional fusions in both L. monocytogenes wild-type (wt) and Delta sigB backgrounds and then measuring (i) beta-glucuronidase (GUS) activities; (ii) gus mRNA transcript levels; and (iii) the presence or absence of GUS in cells by immunofluorescence staining. prfAP2-directed expression increased as the wt L. monocytogenes strain entered stationary phase, whereas prfAP2-directed expression was greatly reduced in the Delta sigB strain, confirming both growth phase- and sigma(B)-dependent transcription of prfAP2. We conclude that prfAP2 is directly regulated by sigma(B). (c) 2005 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.