Uni-Bayreuth grafik-uni-bayreuth


Reiche, M*; Lüdecke, C; Küsel, K: Microbial Iron Cycling at the Oxic-Anoxic Interface in an Acidic Fen
Vortrag, 12th International Symposium on Microbial Ecology - ISME 12, Cairns, Australia: 17.08.2008 - 22.08.2008

Microbial reduction of Fe(III) can be an important process in minerotrophic fens that receive Fe(II) from groundwater flow. Water table fluctuations can lead to an oxygenation of upper peat layers which might renewal the pool of Fe(III). At low pH, aerobic microbial oxidation of Fe(II) can compete successfully with chemical Fe(II) oxidation and form bioavailable Fe(III)-hydroxides. In this study, we investigated the effect of changing redox conditions during the vegetation period of 2007 on microbial iron cycling in an acidic fen (pH ~4.8) located in northern Bavaria, Germany. FeS probes indicated that the oxygenated zone reached down to 20 cm depth followed by highest dissolved Fe(II) concentrations of up to 160 µM. Numbers of aerobic Fe(II)-oxidizers determined by MPN technique were most abundant (10^4 cells per gram peat) in 10-to-20 cm depth indicating that Fe(II) oxidizers used the opposing gradients in this fen. Microelectrode measurements showed that a fast growing enrichment of Fe(II) oxidizers cultured at pH 5 in opposing gradient tubes was highly active at 30 percent oxygen saturation. Anoxic incubations demonstrated that the 0-to-10 cm peat layer had highest Fe(III)-reducing activities. However, numbers of cultured Fe(III) reducers did not decrease with depth and approximated 10^6 cells per gram peat. Amplification of extracted DNA for Fe(III) reducing microorganisms yielded PCR products specific for Acidiphilium- and Geobacter-related sequences. Thus, a tight coupling between microbially induced Fe(II) oxidation and Fe(III) reduction appeared to occur at oxic-anoxic interfaces in this fen.

Letzte Änderung 07.01.2010