Ökologie methanotropher Bakterien: Räumliche Verteilung und Funktion methanotropher Bakterien in Feuchtgebieten.

Methane is the second most important greenhouse gas after CO2 exerting a radiative forcing about a third of that of CO2. Most of the atmospheric methane is released from biogenic sources such as landfills, natural wetlands and rice fields. Methane emission from these sources would be significantly higher without the activity of methanotrophs that oxidize the biogenically produced methane, thus reducing the methane emissions up to 80 %. Consequently, the physiology, diversity and ecology of methanotrophs have been studied. However, influences of biogeographical patterns and spatial hetero-geneities on the methanotrophic community are poorly investigated. Furthermore, little is known about population dynamics and contribution of specific taxa to methane oxidation. The effect of environmental disturbances on the stability and function of microbial communities has just begun to be realized. However, a link between diversity and function and the regulation of methanotrophic communities by natural and/or anthropogenic factors are not known in detail. In this thesis the pmoA gene was used as a functional and phylogenetic marker for the identification of methanotrophs from environmental samples. On a global scale certain pmoA genotypes seem to be specifically adapted to paddy fields while at closely geographically located field sites methanotrophic communities revealed different community patterns. The influence of environmental gradients varies between different habitats and has to be considered when designing experimental studies. In the studied agroecosystem, population structure showed no spatial pattern implying that both a systematic and random sampling design would be adequate. We observed a succession of methanotrophs, however, the oxidation performance stayed relatively stable. Hence, a diverse microbial seed bank of methanotrophs seems to play an important role in maintaining the function in such a dynamic ecosystem. From this seed bank different methanotrophs are activated under high and low energy fluxes. We identified species of the genus Methylobacter and an environmental cluster strictly affiliated with paddy soils that seem to be adapted to high methane environments. Methanotrophic community was not significantly affected by nitrogen fertilization under different energy flows. We suggest that methanotrophs are quite resilient, and that changes in the energy flow have major effects for the community structure.