The <i>Pseudomonas aeruginosa rhlAB</i> Operon Is Not Expressed during the Logarithmic Phase of Growth Even in the Presence of Its Activator RhlR and the Autoinducer <i>N</i> -Butyryl-Homoserine Lactone

Abstract

The Pseudomonas aeruginosa rhlAB operon encodes the enzyme rhamnosyltransferase 1, which produces the biosurfactant mono-rhamnolipid; rhlAB induction is dependent on the quorum-sensing transcription activator RhlR complexed with the autoinducer N-butyryl-homoserine lactone (C(4)-HSL). In this work we studied rhlAB induction in a P. aeruginosa and Escherichia coli background. We found that, in both bacteria, its expression is not induced during the logarithmic phase of growth even in the presence of RhlR and C(4)-HSL. Additionally, we found that rhlAB expression is partially sigma(s) dependent.