Generation and regulation of the electrical membrane potential (Δψ) in Campylobacter jejuni, the major constituent of the proton motive force

The generation of an electrical membrane potential (Δψ), the major constituent of the proton motive force (pmf) is crucial for the ATP synthesis, bacterial growth and motility. The pmf drives the rotation of flagella and is vital for the microaerophilic human pathogen Campylobacter jejuni to colonize the mucus layer of the gut of warm-blooded animals. C. jejuni harbors a branched electron transport chain, enabling respiration with different electron donors and acceptors to generate a Δψ. Here, we demonstrate which electron donor/acceptor couples generate a Δψ and show the impact of the Δψ on the growth performance and motility of this bacterium. In the absence of both oxygen and formate or hydrogen, no Δψ is generated, which strongly reduced the growth rate and the number of motile bacteria. ATP generation is driven either by the pmf, or by substrate level phosphorylation if pyruvate is present. In response to low oxygen tension, C. jejuni upregulates the transcription of the alternative respiratory acceptor complexes and increases the transcription and activity of the donor complexes formate dehydrogenase (FdhABC) and hydrogenase (HydABCD). In conclusion, C. jejuni is dependent on oxygen as electron acceptor or formate/hydrogen as electron donor to generate a pmf that sustains efficient growth and motility performance. Overall design: Comparison of growth conditions, C. jejuni strain 81116 grown under microaerophilic (5% Oxygen) condition compared to C. jejuni strain 81116 grown under oxygen limited (0.3% oxygen) conditions with or without 10mM nitrate.