The relationship between QS and other regulatory pathways. The QS regulon is defined as the collection of genes activated by 3OC12-HSL-LasR or C4-HSL-RhlR, directly or indirectly. The different regulatory pathways shown affect the expression of overlapping subsets within the QS regulon. Effects on signal synthase and receptor expression have not been detailed separately. The bold black lines indicate superregulation of LasR-LasI and RhlR-RhlI. The bold grey lines indicate co-regulation of target genes. PA2591 is one of several predicted transcriptional regulators activated by las QS. This figure has been modified from .