Fermentative metabolism is repressed by Rex during aerobic growth.
A. Model of aerobic and anaerobic central metabolic pathways in L. monocytogenes. Enzymes encoded by genes repressed by Rex are denoted in purple text. Underlined metabolic end-products were those differentially produced by Δrex compared to wt during aerobic growth. LdhA, lactate dehydrogenase; PflABC, pyruvate formate lyase; Lap, alcohol dehydrogenase; ATP, adenosine triphosphate; NAD(H), nicotinamide adenine dinucleotide; ETC, electron transport chain; TCA, tricarboxylic acid cycle. B. Aerobic growth of wt, Δrex, and the complemented strain (Δrex p-rex) measured by optical density (OD600). C-F. Glucose and extracellular metabolites were quantified 4 hours post-inoculation in aerobic (black, blue, and light blue bars) and anaerobic (grey and purple bars) cultures. Concentrations of glucose (C), lactate (D), formate (E), and acetate (F) were determined and normalized to OD600. G. Relative intracellular ATP concentration was measured at 4 hours during aerobic (black, blue, and light blue bars) and anaerobic (grey and purple bars) growth. Data are the means and standard error of the mean (SEM) of three independent experiments in all panels with the exception of panel G. Here, anaerobic samples are the means and SEMs of two independent experiments. p values were calculated using a heteroscedastic Student’s t test. * p < 0.05; ** p < 0.01; **** p < 0.0001; n.s. p > 0.05. In all panels, no significant difference was found between wt and Δrex p-rex. In C-G, no significant difference was found between the wt and Δrex strains grown in anaerobic conditions.
