Effect of different carbon sources on lctP expression.

FA19 reporter strain JC28 and isogenic mutant JC29 (gdhR::kan) containing an lctP-lacZ fusion in vector pLES94-lctP were grown to stationary phase on GC broth supplemented with a concentration range (1.38, 2.75 and 5.50 mM) for each carbon source. Titration of glucose supplemented cultures was done with a fix concentration of 3 mM L-lactate, and titration with L-lactate or pyruvate was done with a fix concentration of 1.5 mM glucose. β-galactosidase was expressed from the lctP transcriptional and translational signals and its activity was determined in Miller units. Data are presented as the mean (bar) plus the standard error of the mean (error bar) of 3 biological samples and two technical replicates each. ** represents significant statistical differences at p<0.01 within each carbohydrate titration group as determined by a non-parametric Kruskal-Wallis test and a Dunn’s posttest.