Two hundred samples were taken from various sites in Iran, including coal storage areas, waste water in the Tabas and Zirab coal mines, and sulphur containing acid springs in Ramsar and Abask , and were screened for Thlobacillus ferruuxidans. During this investigation , seven strains were isolated which could oxidize sdphm , pyrite , thiosdphate and ferrous iron as the sole energy source. Macroscopic, microscopic and biochemical studies showed that the isolates were T. f e r r ooxidans