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Keywords: alkaliphiles, biotechnology, serpentinization, ATP synthase, Bacillus pseudofirmus OF4, bioenergetics, proton-motive force

Multiple strategies are hypothesized to be involved in enabling alkaliphiles to circumvent the challenge of a low bulk proton-motive force energizing proton-coupled ATP synthesis at high pH.

… In the presence of free geochemical proton gradients, protocells in vents can adapt to a sodium-motive force, all the while being powered by a proton-motive force. Eventually, cell membranes became tight to Na+, if not H+. So how did active pumping originate?

… Soon, a Donnan equilibrium is established, in which the electrical charge across the membrane balances the concentration gradient, annulling the proton-motive force. This problem is only unmasked if the membrane can actually hold an electric charge, which is to say, only if the membrane has become impermeable …

… The electron transfer reactions catalyzed by complexes I, III, and IV are coupled to the generation of the proton motive force. The latter is used by ATP synthase (FoF1-ATP synthase or complex V) to produce ATP.

… The proton motive force generated by type I NADH dehydrogenase and the terminal oxidases is used by FoF1-ATP synthase to make ATP [113,114,115]. Being a true proton pump, cytochrome bo3 produces the proton motive force with higher efficiency as compared to the evolutionarily unrelated bd …

This gradient produces the proton motive force (PMF or ∆p), which can be described as a measure of the potential energy stored across the IMM. Since protons are electrically charged particles, the PMF has both chemical and electric components. The electric component corresponds to the voltage difference across …

… This generates the proton-motive force, which is composed of both a pH gradient and the mitochondrial membrane potential (ΔΨm) [4] allowing ATP synthase (complex V) to harnesses this electrochemical gradient to produce ATP.

… The fact that the proton-motive force is more universal today than the sodium-motive force probably derives from evolutionary interpolation of quinones—which are always coupled to proton-dependent redox reactions—on these earlier, necessarily promiscuous origins [205].

… The reversed gradient reduces the trans-membrane proton-motive force available to energize ATP synthesis.

… The resulting loss in proton motive force prevents ADP phosphorylation to ATP at the level of ATP synthase, which rather works in “reverse mode” coupling ATP hydrolysis to proton pumping. The net result is that mitochondria no longer produce ATP and become very powerful in hydrolyzing glycolytic ATP …

… c in a reaction sequence that is referred to as the proton-motive Q-cycle, which contributes to maintaining the proton electrochemical potential across the inner mitochondrial membrane.86 The QH2 electron donor binds in a Q-binding site referred to as QP, which is located near the …

… The resulting proton motive force drives the rotation of the FO sector of ATP synthase leading to the synthesis of ATP in the F1 sector, but the electron flow through the respiratory chain also generates ROS/RNS. In addition, the mitochondrial permeability transition pore (PTP), a large-conductance …

… The finding that such alkaliphilic aerobes use proton-coupled ATP synthases was a surprising finding, since the apparently low bulk proton-motive force (PMF) had led to the expectation that synthesis would be coupled to larger bulk sodium-ion gradients (Hicks and Krulwich, 1990; Krulwich, 1995). The use …