THE POSSIBLE ROLE OF SURFACE-CHARGE IN MEMBRANE ORGANIZATION IN AN ACIDOPHILE

Thiobacillus ferrooxidans, an obligate acidophile, possesses an electr on transport chain that uses oxidation of ferrous iron to generate pro ton motive force. The cells possess an efficient machinery for inter-c onversion of the two components of the free energy, namely pH gradient and membrane potential. incidentally, unlike most of the naturally oc curring membranes, surface in T. ferroxidans appears to be positively charged at or near its physiological pH. independent estimate of such charge was obtained from binding studies with anionic optical and fluo rescent probes. When the external pH is lowered below a critical value the interconversion of the two components of the proton motive force uas no longer operative. A surface charge mediated phase separation of membrane is suggested as one of the possible mechanisms for the failu re of such inter-conversion process.