Importance of balanced intracellular formate levels for pH(i) and CO(2) homeostases during mixed-acid fermentation.

Balanced intracellular formate levels are essential for maintaining pH(i), CO2 homeostasis, and energy metabolism during mixed-acid fermentation in Escherichia coli, with disruptions causing growth defects.

• Why it matters: Understanding how formate imbalance affects cellular processes is crucial because it impacts fermentation efficiency, energy production, and cellular health, which are vital for biotechnological applications and bacterial physiology.
• What they did: The study examined an E. coli mutant with a FocA N209 variant that continuously exports formate, using fermentation profiling, pH measurements, and growth assays to assess metabolic and physiological changes.
• The result: Findings show that formate imbalance elevates intracellular pH, reduces ATP levels, and shifts fermentation toward ethanol at the expense of acetate and succinate, impairing growth and homeostasis.