Man’s interference with the nitrogen cycle causes a rising concentration of N2O in the atmosphere. The ultimate cause is nitrogen enrichment of the biosphere, the proximal N2O sources are nitrogen red/ox reactions by prokaryotes. The relationship between nitrogen enrichment and N2O emission is neither linear nor constant. Instead, it depends on the biochemical functioning of prokaryotes in ecosystems. Thus, there exist options for mitigating N2O emissions provided we know how N2O emissions are regulated at the cellular-, microhabitat-, whole soil-, soil-plant- and ecosystem level. To find such options, we need an amalgam of field observations, modelling and fundamental research on the microbes which produce N2O. The UMB Nitrogen group represents such an amalgam - by virtue.
The main focus of the Nitrogen group is the regulatory biology and ecology of denitrifying prokaryotes, which are the most important source of N2O emission from biosphere to atmosphere. Our studies follow three main tracks and pursue a series of hypotheses based on our conviction that we need to take a more serious look at the “phenotypes” than has been done in the past. Great discoveries have been made by the use of molecular methods in microbial ecology, and the challenge now is to “bridge” from such genetic information to functions in the ecosystem.
Denitrification illustrates our point of view: Most knowledge about the regulatory biology of denitrification is based on biochemical studies of a few “paradigm strains” (Paracoccus denitrificans, Pseudomonas stutzeri). However, these paradigm strains are rare in most natural environments, as revealed by community DNA sequence information. Analyses of community DNA have revealed that soils harbour profoundly different communities, but the predictive capacity of such findings is marginal since the phenotypes are largely unknown!
The group overlaps and collaborates with other research groups at UMB and elsewhere, with expertise in soil physics, soil-plant ecosystem research and modelling, as well as N2O emission monitoring. The aim of these collaborations is to implement novel findings at cellular and community level in dynamic modelling of intact ecosystems (soils). Our endeavours at the laboratory scales can only represent hypotheses; to be tested by a combination of measurements and simulations of N2O emissions at larger scales.
