iNet

Project "iNet" data sheet

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 Project objective

Microbial interactions drive global biogeochemical cycles and shape functionality and productivity of ecosystems. Autotrophic nitrification is a prime example for a mutualistic interplay of two functional groups. In fertilized soils, nitrification contributes to emission of the ozone-depleting greenhouse gas nitrous oxide and nitrogen (N) run-off into surface waters, resulting in eutrophication and algal blooms. In contrast, in biological wastewater treatment it initiates the removal of excess N to reduce the N load into the environment. In their cross-feeding interaction, ammonia-oxidizing bacteria (AOB) provide the electron donor for their partner by converting ammonia to nitrite, which is further oxidized to nitrate by nitrite-oxidizing bacteria (NOB). In addition, nitrifiers also interact with heterotrophic bacteria that feed on metabolites released by nitrifiers or attack them in a predator-prey interaction. In this project, I aim to determine factors defining interaction networks of nitrifiers by analyzing the effect of this interplay on the metabolism of the individual allies and by identifying novel interaction partners of nitrifying microbes. I will analyze the metabolic aspects of this interplay in artificially mixed nitrifying assemblages to simplify the complex interaction networks occurring in nature. Using state-of-the-art isolation techniques, I will first isolate novel AOB and NOB cultures from the same environment to obtain true interaction partners. Physiological key features and gene expression patterns of separately grown and mixed cultures of these isolates will be compared to determine the nature and effects of interactions among nitrifiers. In addition, novel interaction partners of uncultured nitrifiers will be identified by analyzing co-occurrence patterns within spatially structured environments. Overall, this project will greatly expand our understanding of nitrification and the dynamics shaping its stability and process performance.