Transcriptional regulation of the fimbrial operon by the RcsCDB system.

In serovar Typhimurium, the RcsCDB regulatory system controls the expression of genes involved in synthesis of colanic acid, formation of flagella and virulence. Here, we show that activation of the RcsCDB system downregulates expression of an operon that encodes fimbriae involved in attachment to the mucus layer in the large intestine. Bioinformatic analysis predicts the existence of an RcsB-binding site located 180 bp upstream to the +1 transcription start site of the promoter, and electrophoretic mobility shift assays confirm that RcsB binds the promoter region . This study adds RcsB to the list of regulators of transcription and provides an example of modulation of fimbriae synthesis by a signal transduction system.