Geobacter metallireducens —evaluation of its sustainability in nitrate-reducing Fe(II) oxidation under autotrophic conditions

Le résumé fourni par la source

Bacterial nitrate (NO3-) reducing Fe(II) oxidation is often regarded as an autotrophic process, although its long-term sustainability is rarely demonstrated. Here, we assessed whether Geobacter metallireducens (ATCC 53774) can sustain chemolithoautotrophic nitrate-reducing Fe(II) oxidation. Cultures were incubated with Fe(II) and NO3- as electron donor and acceptor, respectively, and CO2 as the sole carbon source. Negative controls contained either (1) electron acceptor, (2) donor or (3) no substrates. We found that first-generation cultures transferred from a washed NO3-/acetate-grown preculture oxidized 21.0±1.3% (2.09±0.14 mM) of 10 mM Fe(II) and reduced 5.2±3.9% (0.20±0.15 mM) of 4 mM NO3-. Nitrite remained below the detection limit and ammonium increase was not observed while total N2O accumulated up to 31.34±1.90 µM. However, following transfers under organic-free conditions did not sustain Fe(II) oxidation. Further, we did not observe a decrease in nitrate, although we found low N2O formation of total 9.10±0.42 µM and 14.10±3.90 µM in later generations. These results demonstrate that G. metallireducens does not sustain autotrophic nitrate-reducing Fe(II) oxidation, although it may contribute to coupled Fe(II) oxidation and nitrate reduction in organic environments.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.