Formate increases the F₀F₁-ATPase activity in Escherichia coli growing on glucose under anaerobic conditions at slightly alkaline pH

Escherichia coli growing on glucose under anaerobic conditions at slightly alkaline pH carries out a mixed-acid fermentation resulting in the production of formate among the other products that can be excreted or further oxidized to H₂ and CO₂. H₂ production is largely dependent on formate dehydrogenase H and hydrogenases 3 and 4 constituting two formate hydrogen lyases, and on the F₀F₁-ATPase. In this study, it has been shown that formate markedly increased ATPase activity in membrane vesicles. This activity was significantly (1.8-fold) stimulated by 100mM K⁺ and inhibited by N,N^′-dicyclohexylcarbodiimide and sodium azide. The increase in ATPase activity was absent in atp, trkA, and hyf but not in hyc mutants. ATPase activity was also markedly increased by formate when bacteria were fermenting glucose with external formate (30mM) in the growth medium. However this activity was not stimulated by K⁺ and absent in atp and hyc but not in hyf mutants. The effects of formate on ATPase activity disappeared when cells were performing anaerobic (nitrate/nitrite) or aerobic respiration. These results suggest that the F₀F₁-ATPase activity is dependent on K⁺ uptake TrkA system and hydrogenase 4, and on hydrogenase 3 when cells are fermenting glucose in the absence and presence of external formate, respectively.