INTERCONVERSION OF CHEMIOSMOTIC PARAMETERS AND ITS INHIBITION IN THIOBACILLUS-FERROOXIDANS

In Thiobacillus ferrooxidans, an iron oxidizing obligatory acidophilic bacterium, bioenergetics was found to be critically dependent oil sul phate distribution across its membrane, Under physiological condition, file sulphate distribution was found to be far from its electrochemic al equilibrium, and a high residual proton motive force (similar to 11 0 mV) remained conserved under varying, external pH even in respiratio n-starved cells, Thc inter-conversion between bioenergetic parameters, namely membrane potential nod pH gradient, was inhibited at a critica l, low pH Below this critical pH, proton-coupled sulphate influx was o bserved, as measured by radio-labelled transport assay, leading to col lapse of the two chemiosmotic gradients, The associated alteration of membrane structure and permeability property was monitored by intrinsi c fluorescence of T. ferrooxidans and extrinsic fluorescent probes.