English: Methods of pH homeostasis and energy generation in acidophiles (with reference to Baker-Austin & Dopson, 2007 and Apel, Dugan, & Tuttle, 1980):

(1) Direction of transmembrane electrochemical gradient (pH) and blocking of H+ by the cell membrane; (2) Reversed membrane potential through potassium transport, a modification towards maintaining a stable Donnan potential; (3) Secondary transporter protein; the H+ and Na+ gradient is harnessed to drive transport of nutrients and solutes; (4) Proton pump actively removes H+, balancing the energy gained from the H+ entry to the cytoplasm. (5) Vesicles containing protons avoid acidification of the cytoplasm, but still generate ATP from the electrochemical gradient (in A.ferrooxidans); (6) Uncouplers (uncharged compounds), such as organic acids, permeate the membrane and release their H+, leading to acidification of the cytoplasm; (7) To avoid this, heterotrophic acidophiles may degrade the uncouplers;

(8) Alternatively, cytoplasmic enzymes or chemicals may bind or sequester the protons.