Adaptive reduction of a Pseudomonas aeruginosa quorum sensing regulon

Many bacteria use quorum sensing (QS), a cell-cell communication system, to regulate the expression of genes in a cell-density-responsive manner. The QS regulon of P. aeruginosa has been shown to include hundreds of genes under regulation of the acyl homoserine lactone (AHL) -responsive signaling systems LasR-I and RhlR-I. Here we used the AHL-degrading enzyme AiiA-lactonase to interrogate the evolution of the LasR-dependent QS regulon in conditions where QS is required to obtain carbon and energy and show that populations of P. aeruginosa adaptively reduced the size of their QS regulon over ~1000 generations.