GENERAL MICROBIOLOGY - T.P. Pyrog - 2004

16. UTILIZATION OF INORGANIC HYDROGEN DONORS: AEROBIC CHEMOLITHOTROPHIC BACTERIA

16.3. FERROUS IRON OXIDATION

The iron bacterium Thiobacillus ferrooxidans oxidizes ferrous iron to ferric iron:

Class="center">

This bacterium is very similar to Thiobacillus thiooxidans, remaining viable at pH levels down to 2.5, but it can derive energy not only from the Oxidation of reduced sulfur compounds, but also from The oxidation of iron. It inhabits acidic mine waters containing sulfides of various metals, including pyrite (FeS2).

Iron oxidation is also carried out by the sulfur-oxidizing bacterium Sulfolobus acidocaldarius. Other iron Bacteria (excluding sulfur oxidizers) include Gallionella ferruginea and Leptothrix ochracea, which can be found in drainage pipes and mountain streams amidst layers of iron oxide.

Leaching (bioleaching) of metals from ores. The ability of certain acidophilic sulfur- and iron-oxidizing bacteria to convert sulfides and elemental sulfur into Water-soluble heavy metal sulfates is utilized for leaching low-grade ores to recover copper, zinc, nickel, molybdenum, and uranium. The simplest method involves passing water through a thick layer of crushed rock containing ore (e.g., pyrite FeSz) along with associated metal sulfides, followed by collecting the sulfate-containing solution. After concentration of this solution, the metals are precipitated from it.

The dissolution of heavy metal sulfides occurs through the simultaneous action of multiple processes:

1) bacterial oxidation of reduced sulfur compounds or elemental sulfur to sulfuric acid

2) bacterial Oxidation of ferrous iron to ferric iron

3) chemical oxidation of insoluble heavy metal salts to soluble sulfates and sulfur

Thus, bacteria supply sulfuric acid and also regenerate Fe3*. Both of these components are consumed in ore bioleaching. These transformations are mediated by Thiobacillus ferrooxidans and Thiobacillus thiooxidans. Certain strains of these bacteria exhibit remarkable resistance to relatively high concentrations of copper, cobalt, zinc, and other heavy metals.



Last update: 12/08/2026

Editorial and Educational Adaptation: This material has been compiled based on the primary/original source text. The project team performed an editorial review, corrected technical inaccuracies, structured sections, and adapted the content for an educational format.

What was processed:

  • elimination of formatting defects (OCR errors, structural breaks, corrupted characters);
  • editorial organization of content;
  • standardization of terminology in accordance with academic sources;
  • verification of factual statements against the original source text.

All mentions of the author, publication year, and origin of the primary text have been preserved in accordance with the source.