How fdhF Deletion Affects Ion Transport and ATPase Activity in E. coli?

Abstract

Formate dehydrogenase-H plays a key role in anaerobic metabolism, particularly in formate metabolism during fermentation. To assess its glucose-dependent role, proton (J_H⁺) and potassium (J_K⁺) fluxes, along with F_OF₁-ATPase activity, were examined in wild-type and fdhF mutant grown under low (2 g L⁻¹) and high (8 g L⁻¹) glucose. When cells were grown in the presence of low glucose and during assays similar amount was added mutant showed 40% higher J_H⁺ but 30% lower F_OF₁-conditioned flux, consistent with a 20% reduction in ATPase activity upon potassium supplementation, but there were no differences when extra formate, or potassium and formate together were supplemented. At the same time total J_K+ was lower compared to wild type, meanwhile DCCD does not affect the flux. Under high glucose, mutants displayed a 50% increase in total and DCCD-sensitive J_H⁺ fluxes, a 35% decrease in J_K⁺, and a 50% drop in F_OF₁-conditioned flux. When cells were grown in a presence of high glucose and during assays similar amount was supplemented total J_H+ was similar in mutant and wild type, meanwhile DCCD-sensitive flux decreased by 25-35%, conversely total J_K+ increased by 35% and with DCCD potassium outflux was observed. Potassium had no effect on ATPase activity, but formate increased it by 25%. These findings suggest that under low glucose, accumulated formate stimulates proton efflux while inhibiting ATPase, whereas under high glucose, formate regulates ATPase via potassium, highlighting a glucose-dependent shift in formate’s control of membrane bioenergetics.