Negative Regulation of Violacein Biosynthesis in Chromobacterium violaceum

In <i>Chromobacteium violaceum</i>, the purple pigment violacein is under positive regulation by the <i>N</i>-acylhomoserine lactone CviI/R quorum sensing system and negative regulation by an uncharacterized putative repressor. In this study we report that the biosynthesis of violacein is negatively controlled by a novel repressor protein, VioS. The violacein operon is regulated negatively by VioS and positively by the CviI/R system in both <i>C. violaceum</i> and in a heterologous <i>Escherichia coli</i> genetic background. VioS does not regulate the CviI/R system and apart from violacein, VioS, and quorum sensing regulate other phenotypes antagonistically. Quorum sensing regulated phenotypes in <i>C. violaceum</i> are therefore further regulated providing an additional level of control.