Increase in Fe²⁺-Producing Activity during Growth of Acidithiobacillus ferrooxidans ATCC23270 on Sulfur

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When Acidithiobacillus ferrooxidans ATCC23270 cells, grown for many generations on sulfur were grown in sulfur medium with and without Fe³⁺, the bacterium markedly increased not only in iron oxidase activity but also in Fe²⁺-producing sulfide:ferric ion oxidoreductase (SFORase) activity during the early log phase, and retained part of these activities during the late log phase. The activity of SFORase, which catalyzes the production of Fe²⁺ from Fe³⁺ and sulfur, of sulfur-grown cells was approximately 10–20 fold higher than that of iron-grown cells. aa₃ type cytochrome c oxidases, an important component of iron oxidase in A. ferrooxidans, was partially purified from sulfur-grown cells. A. ferrooxidans ATCC23270 cells grown for many generations on sulfur had the ability to grow on iron as rapidly as that did iron-grown cells. These results suggest that both iron oxidase and Fe²⁺-producing SFORase have a role in the energy generation of A. ferrooxidans ATCC23270 from sulfur.