Uni-Bayreuth grafik-uni-bayreuth


Reiche, M*; Küsel, K: Microbial Reduction of Iron(III) in a Methane-emitting Acidic Fen (updated)
Poster, Jahrestagung der Deutschen Gesellschaft für Limnologie (DGL), Dresden: 25.09.2006 - 29.09.2006

Northern peatlands are considered to be significant sources of methane, and H2 appears to be the dominant precursor for methanogenesis in slightly acidic peatlands. However, Fe(III)-reducing bacteria may suppress methanogenesis by competition for H2 or acetate, and methanogens may divert electrons to Fe(III). It was the aim of this project (i) to compare Fe(III)-reducing and methanogenic activities in a slightly acidic fen in the Fichtelgebirge, Bavaria, and (ii) to enumerate Fe(III)-reducing microbiota with MPN technique. Anoxic incubation experiments demonstrated that the reduction of Fe(III) occurred in the upper (0-10 cm) zone with a rate of approximately 4 µmol Fe(II) * g (fresh weight soil)-1 * d-1. Although high amounts of Fe(II) were present in deeper zones, there was no on-going Fe(III)-reducing activity. Methanogenesis had its maximum in 30 to 40 cm depth. In the presence of methyl fluoride, a selective inhibitor of acetoclastic methanogenesis, the formation of methane was inhibited by more than 50% indicating that acetate might be also an important precursor for the formation of methane in this fen. The local activity differences were supported by depth profiles of Fe(II), sulfate, and methane in the fen soil water. Numbers of acetate-, ethanol-, or lactate utilizing Fe(III)-reducing bacteria cultured at pH 5.5 approximated 10^5 to 10^6 cells g (fresh weight soil)-1 and decreased negligible with soil depth. Numbers of fermentative glucose-utilizing Fe(III)-reducers were most abundant indicating that fermenting bacteria might contribute substantially to the reduction of Fe(III) which appeared to be an important alternative electron acceptor for the oxidation of organic matter in upper zones of this acidic fen.

Letzte Änderung 02.11.2006