Fig. 4: ComK upregulates glycolysis in S. aureus cells.

A Simplified representation of the S. aureus glucose catabolic pathway. Glucose is catabolized to pyruvate, which can be reduced to lactate, 2,3 butanediol (2,3 Bd) or acetyl-CoA. In the presence of high glucose levels, acetyl-CoA is converted to acetate via fermentation (blue arrow) to produce ATP; respiratory chain activity is thus reduced. Lower glucose levels redirect acetyl-CoA towards the TCA cycle. The NADH generated in glycolysis and the TCA cycle is oxidized via the respiratory chain to restore the redox balance and to produce ATP. The genes coding for glycolytic enzymes that are upregulated by comK are shown in green. B Determination of glucose levels in supernatants of H₂O₂-treated cultures. Concentration is represented in relation to culture OD₆₀₀. Statistical significance was measured by one-sided ANOVA with Tukey’s test for multiple comparison. Data are shown as mean ± SD of three independent experiments (n = 3). C Genetic pathway to acetate production. (i) Overflow metabolic pathways to acetate production in S. aureus. Under aerobic conditions, acetyl CoA is converted to acetate by the Pta (phosphotransacetylase)/AckA (acetate kinase) route. Excess glucose activates an additional route that diverts pyruvate towards acetate production via pyruvate oxidase (CidC). (ii) qRT-PCR analysis of ackA and cidC gene expression in the H₂O₂-treated S. aureus strains. Differences were examined by one-sided ANOVA with Tukey’s test for multiple comparison; **p < 0.01. Data are shown as mean ± SD of three independent experiments (n = 3). D Determination of acetate (left panel) and lactate (right panel) levels in culture supernatants of H₂O₂-treated TSB cultures. Concentration is represented in relation to culture OD₆₀₀. Statistical significance was measured by one-sided ANOVA with Tukey’s test for multiple comparison. Data are shown as mean ± SD of three independent experiments (n = 3). E Determination of oxygen consumption rate in H₂O₂-treated TSB cultures over time. Statistical significance was measured by one-sided ANOVA with Tukey’s test for multiple comparison. Data are shown as mean ± SD of three independent experiments (n = 3). F Determination of intracellular NADH and NAD⁺ in the S. aureus strains. Results are presented as the NADH/NAD⁺ ratio for the different strains in relation to the WT. One-sided ANOVA; **p < 0.01. Data are shown as mean ± SD of three independent experiments (n = 3). G Determination of intracellular ATP levels in S. aureus cultures collected during the exponential (EX) and stationary phase (SS). ATP levels of the different strains are represented in relation to WT levels. Comparisons were made using one-sided ANOVA with Tukey’s test for multiple comparisons; *p < 0.05. Data are shown as mean ± SD of three independent experiments (n = 3). Source data are provided as a Source Data file.