Fig. 2.

(R)-3-HB induced expression of a PA2004-lacZ reporter in P. aeruginosa PAO1. P. aeruginosa PAO1 harbouring a PA2004-lacZ reporter was grown to an OD₆₀₀ of 0.3 in M63 minimal medium supplemented with 30 mM succinate and subsequently challenged with (a) various concentrations of (R)-3-HB or (b) various substrates provided at final concentrations of 1.0 mM. LacZ activity was measured 30 min post-addition of substrate. As shown, racemic and enantiopure (R)-3-HB were the only compounds that induced expression of the PA2004-lacZ reporter (twofold increase in LacZ activity). Notably, a concentration of 500 μM (R)-3-HB was found to be sufficient to induce expression of PA2004-lacZ. Data points represent mean values ± sd (n = 4). ANOVA was performed using a Dunnett's post-hoc test (α-value of 0.05) to identify significant changes (P <  0.0001), which are marked with an asterisk.