Das Projekt "Die Oekologie rhizospaerer bakterieller Gemeinschaften bei zwei ausdauernden Graesern mit unterschiedlichen trophischen Beduerfnissen, Lolium perenne und Molinia coerulea: Auswahl von das Pflanzenwachstum foerdernden Rhizobakterien (PGPR) und Reaktion auf eine CO2-Konzentration in der Luft" wird vom Umweltbundesamt gefördert und von Universite de Neuchatel, Faculte des Sciences, Institut de Botanique, Laboratoire de Microbiologie durchgeführt. The rhizosphere is the exchange interface of plant roots with soil. These exchanges are modulated by the presence of either beneficial or detrimental microorganisms, bacteria and fungi. Hence, microbial biodiversity, in its genetical and functional aspects, is the 'hidden face' of plant biodiversity. Nevertheless, there is a considerable lack of knowledge on the behaviour of microbial communities at the rhizosphere level, particularly on perennial herbaceous plants, which for most of the non-forest wild ecosystems. The present project is focussed on the study of microbial communities in the rhizosphere of two perennial, hemicryptophytic grasses: Lolium perenne, a species requiring N-rich soils, and Molinia coerulea, an oligotrophic species. Within this frame, the project will have two main objectives: - First, a study of rhizosphere or root-inhabiting communities in both grasses in field conditions. So far, similar studies have been carried out almost exclusively on annual crop plants in agro-ecosystems. The bacterial communities present in the rhizosphere of Molinia coerulea in its wildlife habitats will be compared to the communities associated with Lolium perenne in artificial cultures. Special attention will be given to differences that could be associatedwith the different ecological niches occupied by the two plant species. The response of these communities to a CO2 increase will be situated in the prospect of forewarnings of a longer-term change in the response of plant communities. - Second, an in depth study of the populations of fluorescent pseudomonads (FLPs), an important group of root-associated bacteria FLPs may have different functions in their relationships with the root: adhesion and/or invasion, parasitism or growth-promotion (plant growth-promoting rhizobacteria, PGPR), dinitrogen fixation, synthesis of antibiotics, induction of plant synthesized metabolites or of enzymes that are antagonist to fungal pathogens. During the foregoing project, these FLPs have been shown to be the dominating organisms in the root fractions of Lolium perenne. This dominance was increased under an artificially CO2-enriched atmosphere (Free Air Carbon dioxide Enrichment - FACE system). We will therefore study the FLPs populations selected by the rhizosphere/root system of both perennial grasses, the activities associated with the selected populations, and their response to a CO2 increase.