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Hamberger, A*; Drake, HL; Horn, M: Structure and Function of Fermenters and Methanogens in an Acidic Fen
Poster, International Symposium Soil processes under extreme meteorological conditions, Bayreuth: 2007-02-25 - 2007-02-28

Acidic wetlands harbor approximately 30% of the global reserves of soil carbon, emit methane, and are characterized by highly dynamic, steep oxic-anoxic gradients depending on water table. Carbon flow to methane proceeds primarily via fermentation and methanogenesis under reduced conditions and is thus highly susceptible to changes in water table and redox potential. However, the microbial community composition of fermenters and methanogens involved in the carbon flow in acidic fens is still largely unresolved. Effects of changes in redox potential on such communities and associated carbon flow, which are induced by drying and rewetting, are not yet understood. Fermenters and methanogens were identified in the acidic fen Schlöppnerbrunnen (Waldstein, Fichtelgebirge, Bavaria, Germany) by cultivation-dependent (enrichments, isolation) and –independent approaches (Stable Isotope Probing, 16S rRNA analysis) to develop a system phylochip for rapid detection of those communities. Cultivation-dependent approaches revealed that members of the genera Sphingomonas, Pelobacter, Clostridium, Propionispira (104 cells [g fw]-1), Buchnera (105 cells [g fw]-1), Serratia (106 cells [g fw]-1), Desulfuromonas (108 cells [g fw]-1), and Pseudomonas (1010 cells [g fw]-1) were abundant fermenters in the acidic fen, indicating that obligate anaerobes and facultative aerobes were involved in fermentation. Glucose, xylose, and ethanol were converted to fatty acids, CO2, H2, and CH4 in microcosms, indicating that the acidic fen harbored glucose-, xylose-, and ethanol- using fermenters. 16S rRNA-based stable isotope probing indicated that such organisms were members of the genera Pseudomonas and Clostridium. New members of the methanogenic archaeal genera Methanosarcina, Methanobacterium, and Methanopyrus were active in anoxic microcosms, showing that the acidic fen harbored potentially new methanogens. Analysis of 16S rRNA genes by fingerprinting methods (DGGE) and clone libraries showed that the detectable bacterial community was more diverse than the archaeal community over depth (0-40 cm) at all sampling sites. Members of the phyla Euryarchaeota (Thermoplasmatales, methanogenic Methanomicrobiales, and Methanosarcinales) and Crenarchaeota (Group I.1c) were detected. These results indicate that methanogens, obligate anaerobes, and facultative aerobes are involved in carbon flow in the acidic fen and are thus targets for the development of the system phylochip.

last modified 2007-03-19