FIG 2 .
l-Arg is a potent chemoattractant for P. aeruginosa but reduces swimming motility at high concentrations. (A) Standard tryptone swim plates were supplemented with the indicated concentration of l-Arg. PAO1 swimming motility was significantly increased in the presence of 100 mM l-Arg by one-way ANOVA with Bonferroni’s multiple comparison posttest. ***, P < 0.001 (n = 6 to 9 replicates/group). PAO1 swimming motility was significantly reduced in the presence of 250, 500, and 750 mM l-Arg by one-way ANOVA with Bonferroni’s multiple comparison posttest. ***, P < 0.001 (n = 6 to 9 replicates/group). (B) Evaluation of PAO1-GFP swimming-mediated chemotaxis was carried out in an agarose gel-based two-layer microfluidic device. The cell density profile of PAO1-GFP was measured by the fluorescence intensity within the region of interest (ROI) in the observation well for the response toward the indicated concentration of the positive control, l-Ser, or l-Arg. The negative control consisted of buffer alone (1× PBS supplemented with 5 mM MgSO4 and 15 µM EDTA).