Fig. 3.

HirR-HirI constitute a quorum-sensing circuit, and P. putida can use exogenous phenylacetate for PA-HSL synthesis. (A) PA-HSL–dependent hirI promoter activity requires HirR. Expression of hirI::mCherry P. putida containing pLL1 (filled circles), or pLL2 (open circles). There is a hirR gene in pLL1 but not in pLL2. Data are the mean, and the errors bars indicate the range of three biological replicates. (B) HPLC analysis of PA-HSL produced by P. putida (pHirI) grown in MSB broth with (open circles) or without (filled circles) 0.1 mM phenylacetate. The dashed line shows the methanol gradient.