The Relationship between Chemiosmotic Parameters and Sensitivity to Anions and Organic Acids in the Acidophile Thiobacillus Ferrooxidans

We investigated the relationships between the trans-cytoplasmic-membrane chemiosmotic parameters, viz. the membrane potential and the pH difference, and the toxicity of anions and organic acids in the acidophile Thiobacillus ferrooxidans. Organic acids accumulated in the cytoplasm in response to the transmembrane pH difference and inorganic anions could be caused to accumulate in response to the membrane potential. The distribution of the organic acids was unaffected by the membrane potential and that of the anions was not influenced by the pH difference. These accumulations may be toxic because of a direct effect of a high concentration of the anion in the cytoplasm or by acidification of the cytoplasm. The point of inhibition of respiration was at the level of the respiratory chain cytochrome oxidase when Fe(II) was the respiratory substrate.