, Volume 164, Issue 4, pp 294-300

The potential for diazotrophy in iron-and sulfur-oxidizing acidophilic bacteria

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Acetylene reduction was observed with ferrousiron-oxidizingThiobacillus ferrooxidans, as expected from previous studies with this bacterium. Acetylene reduction was also found during the growth ofT. ferrooxidans on tetrathionate. OnlyLeptospirillum ferrooxidans, one of several other phylogenetically diverse, ferrous-iron-and/or sulfur-oxidizing acidophilic microorganisms, also reduced acetylene. A reduction of the oxygen concentration in the culture atmosphere was necessary to alleviate inhibition of nitrogenase activity. DNA sequences homologous tonif structural genes were found in both organisms. Diazotrophic growth ofL. ferrooxidans was inferred from an increase in iron oxidation in ammonium-free medium when the oxygen concentration was limited and from apparent inhibition by acetylene under these conditions.