Evolution of the quorum sensing regulon in cooperating populations of Pseudomonas aeruginosa

We used the AHL-degrading enzyme AiiA-lactonase to interrogate the evolution of the LasR-dependent QS regulon of P. aeruginosa 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. Using a metatranscriptomic approach, we compared the QS-activated regulons of two PAO1-derived populations from early and late timepoints of a 160-day CAM evolution experiment using three treatment regimes: LB-grown cultures were prepared as (i) “plus AiiA lactonase” with added AiiA in 250 ul protein buffer (100 ug/ml final AiiA concentration), (ii) “natural AHL accumulation” with 250 ul of protein purification buffer, and (iii) “plus AHLs” with added 2 uM 3OC12-HSL and 10 uM C4-HSL plus 250 ul of protein purification buffer. Two biological replicates were prepared for each sample condition.