Proton conductance and regulation of proton/potassium fluxes in Escherichia coli FhlA-lacking cells during fermentation of mixed carbon sources.

Escherichia coli uptake potassium ions with the coupling of proton efflux and energy utilization via proton FF-ATPase. In this study contribution of formate hydrogen lyase (FHL) complexes in the proton/potassium fluxes and the formation of proton conductance (CH) were investigated using fhlA mutant strain. The proton flux rate (J) decreased in fhlA by ∼ 25 % and ∼70 % during the utilization of glucose and glycerol, respectively, at 20 h suggesting H transport via or through FHL complexes. The decrease in J in fhlA by ∼40 % proposed the interaction between FHL and Trk secondary transport system during mixed carbon fermentation. Moreover, the usage of N,N'-dicyclohexylcarbodiimide (DCCD) demonstrated the mediation of FF-ATPase in this interaction. CH was 13.4 nmol min mV in WT at 20 h, which decreased by 20 % in fhlA. Taken together, FHL complexes have a significant contribution to the modulation of H/K fluxes and the CH  for efficient energy transduction and regulation of the proton motive force during mixed carbon sources fermentation.