The Specificity of the Anionic Requirement for Iron Oxidation by Thiobacillus ferrooxidans

Abstract

The anionic requirement for the oxidation of ferrous ions by suspensions of Thiobacillus ferrooxidans was satisfied by selenate as well as sulphate. Selenate was toxic to the organism and suppressed growth in ferrous iron media, even in the presence of high concentrations of sulphate. After treatment with dilute hydrochloric acid at o "C, T. ferrooxidans, which specifically required S042-or Se042-for iron oxidation, showed no activity in response to 12 other anions tested. However, after the introduction of or Se042-, addition of anions such as Te0,2-, WO2-, AS043-or Po43-further enhanced the rate of iron oxidation. Under these conditions, C1-, B40,2-and C103-had no significant effect at low concentration, whereas Br-, NO3-and Mo02-were inhibitory. These observations distinguish between a specific and a non-specific anionic requirement for the oxidation of ferrous ions by T. ferrooxidans. The specific requirement is satisfied only through the uptake of S042-or SeOd2-by the bacteria. The non-specific requirement is satisfied by any one of several anions, including SO,2-and Se0,2-, which are presumed to act as ligands for iron in solution.

Selective Inhibition of the Oxidation of Ferrous Iron or Sulfur in Thiobacillus ferrooxidans

“…This apparent preferential inhibition of sulfur oxidation at high sulfate concentrations is believed to be caused by changes in osmotic pressure, as it was observed in all other buffers at high concentrations (Fig. 1) except nitrate, a specific inhibitor of iron oxidation (17), as discussed below. High osmotic pressure inhibited sulfur oxidation in all the buffers tested both with iron-grown (Fig.…”

“…It was initially believed to act as a bridging ligand between ferrous iron and the cell (16,17). Further experiments showed its role in the transfer of electrons from an iron sulfur cluster to the copper(II) ion of rusticyanin in the oxygen-dependent iron oxidation electron transport chain (8).…”

“…Chloride is a known inhibitor of cell growth and ferrous iron oxidation (17,26). It is an inhibitor of cell-free iron-cytochrome c reductase (6).…”

“…T. ferrooxidans was initially isolated from acidic copper-leaching waters and believed to be the dominant bacterium responsible for metal sulfide solubilization (18). Iron oxidation in response to pH (1,28), organic acids (40), anions (2,17), and cations (21,38) has been extensively studied. Sulfur oxidation has received substantially less attention, with limited references to certain anions (26).…”

Microbial Sensor for the Determination of Ascorbic Acid Based on the Iron-Oxidizing Activity of Thiobacillus Ferrooxidans.

“…T. ferrooxidans is one of the most important microorganisms for the bacterial leaching of sulfide ores (Konishi et a/., 1990(Konishi et a/., , 1992 and for the microbial desulfurization of coal (Kargi, 1982). Therefore, a number of studies have been done to understand the basic physiology of T ferrooxidans (Lazaroff, 1963;Sugio et a/., 1985). Recently, the ability of T. ferrooxidans to oxidize Fe2+ has been utilized for iron determination based on the measurement of oxygen consumption in a compact microbia] sensor system (Mandl and Machol~n, 1990).…”