The opportunistic pathogen Pseudomonas aeruginosa is known for its ability to secrete a variety of virulence factors during infection. Expression of these virulence factors is, in many cases, under the control of quorum sensing (QS). Through QS, bacteria such as P. aeruginosa coordinate their gene expression in response to their cell density. The complex network of genes coordinated by QS relies on the activity of the transcription factors LasR, RhlR, and PqsR. These transcription factors bind to their cognate signal or autoinducer: OdDHL, BHL, and PQS, which activate them to elicit changes in gene expression. However, it has recently been proposed that these molecules can also modulate other cellular activities by directly binding to other targets in the cell, thereby modifying protein activity. To test this hypothesis, we are implementing a state-of-the-art proteomic approach: Proteome Integral Solubility Alteration, PISA. This technique - which is based on “thermal proteome profiling” - relies on the change in protein thermal stability when it is bound to a ligand. At the time of writing, and using PISA, we have investigated possible novel binding partners for the two N-acyl homoserine lactone signals used by P. aeruginosa QS; OdDHL and BHL.  So far, we have identified ~ 500 proteins whose stability is altered in the presence of these autoinducers, including transcription factors and enzymes. Our objective now is to validate our findings through in vitro and in vivo experiments.