Impact of a Novel PagR-like Transcriptional Regulator on Cereulide Toxin Synthesis in Emetic .

The emetic type of foodborne disease caused by is produced by the small peptide toxin cereulide. The genetic locus encoding the Ces nonribosomal peptide synthetase (CesNRPS) multienzyme machinery is located on a 270 kb megaplasmid, designated pCER270, which shares its backbone with the toxin plasmid pXO1. Although the genes are plasmid-borne, the chromosomally encoded pleiotropic transcriptional factors CodY and AbrB are key players in the control of transcription. Since these proteins only repress cereulide synthesis during earlier growth phases, other factors must be involved in the strict control of expression and its embedment in the bacterial life cycle. genome analysis revealed that pCER270 carries a putative ArsR/SmtB family transcription factor showing high homology to PagR from . As PagR plays a crucial role in the regulation of the protective antigen gene , which forms part of anthrax toxin, we used a gene-inactivation approach, combined with electrophoretic mobility shift assays and a bacterial two-hybrid system for dissecting the role of the PagR homologue PagRBc in the regulation of cereulide synthesis. Our results highlight that the plasmid-encoded transcriptional regulator PagRBc plays an important role in the complex and multilayered process of cereulide synthesis.