Professor Sang Yoon Kim¹, MS Marion   Meima-Franke², Professor Adrian Ho³, Professor Hyo-Jung  Lee⁵, Professor Lubos Polerecky⁴, MS Michiel   Kienhuis⁴, Ms student Ju-Hee Lee¹, Doctor Paul Bodelier²

¹Department of Bio-environmental Sciences, Sunchon National University, Suncheon, Republic of Korea, Suncheon, South Korea, ²Netherlands Institute of Ecology (NIOO-KNAW), Department of Microbial Ecology, Wageningen, the Netherlands, Wageningen, the Netherlands, ³Institute for Microbiology, Leibniz Universität Hannover, Hannover, Germany , ⁴Department of Earth Sciences, Geochemistry Faculty of Geosciences, Utrecht University  , Utrecht, the Netherlands, ⁵Department of Biology, Kunsan National University, Gunsan, Republic of Korea

Nitrogen is an essential element to all living organisms and is closely linked to the carbon (C) cycle by influencing microbial activities and plant growth characteristics. Changes in N availability may alter methane dynamics by affecting the abundance and composition of methanogenic archaea and methane-oxidizing bacteria in wetland ecosystem. Diazotrophic methanogens and methanotrophs which are capable of fixing atmospheric N2 may play an important role to maintain methane cycling, supplying additional N source in N-limited wetland condition such a rhizosphere. However, it is still unclear which diazotrophic methanogens and methanotrophs are able to fix N2 actively and their contributions to methane cycling in the N-limited wetland soils have not been investigated yet. We investigated the performance of methane cycling microbes under nitrogen-limiting conditions with a special focus on N2 fixation. To create nitrogen limitation condition, we used a planted (Glyceria maxima) microcosm system with separated root- and bulk soil compartments filled with sediment from an agricultural ditch. Actively N2 fixing methanogens and methanotrophs were screened in situ as well as in vitro by mRNA based assessment of nifH genes as well as by using stable isotopes (13C and 15N) in combination with fluorescent in situ hybridization and Nano scale secondary ion-beam mass spectrometry (NanoSIMS) of extracted cells. Methane emission was significantly lower in the absence of fertilizer. Both, growth and activity of methanogens and methanotrophs were reduced by limited by nitrogen availability. NanoSIMS of individual cells indicated that methanogens as well as methanotrophs are actively fixing N2 but at a very low level. Our results suggest that nitrogen availability is a strong regulating factor of methane emission from agricultural and natural wetlands and should be incorporated in methane emission models.

Biography: To be confirmed.