The environmental deposition of nitrogen used in food production and from fossil fuel combustion exceeds the amounts of biologically fixed nitrogen in terrestrial or marine ecosystems¹. Most of the human nitrogen depositions are industrially produced nitrogen fertilizers. Without their application, less than 50% of the current global population would have enough food². A downside of industrialized agriculture is that enormous amounts of ammonium from synthetic fertilizers and manure enter the nitrogen cycle via nitrification. As a result, the nitrogen cycle has reached a high-risk level of perturbation³. Consequences are the eutrophication of ground- and surface waters, dead zones in marine and freshwater systems, and a massive loss of biodiversity. In this precarious situation, management strategies are needed to ensure a more efficient use of fertilizers and to reduce emissions of the highly potent greenhouse gas N₂O, a by-product of nitrogen cycle processes including nitrification.

These important measures to secure the health of our planet are hampered by surprisingly large gaps in our fundamental understanding of the microbiology of nitrification. This is best illustrated by the surprising discovery of comammox bacteria, global players in nitrification that were undetected for more than a century of research^4-7. The identification of comammox has raised pressing questions about the biochemistry, physiology, and ecology of these organisms⁸ - questions that are a true challenge for research, because comammox are elusive bacteria and escape most attempts to grow them under laboratory conditions.

In the Comammox Research Platform we will investigate key aspects of comammox biology, taking advantage of the broad diversity of scientific disciplines at the University of Vienna. Selected key enzymes of comammox will be structurally and biochemically characterized. How does complete nitrification work in a single organism? What are mechanistic differences between comammox and canonical nitrifying microbes? The environmental impact of comammox will be studied by combining approaches from microbiology, chemistry, and ecosystem science. How much do comammox bacteria contribute to nitrification in soils and sewage treatment plants? Does their activity cause environmentally relevant N₂O emissions? Our aim is to achieve an encompassing picture of comammox bacteria over different scales, which range from details of their unique molecular machinery to their roles within microbial communities and ecosystems.

Cited Literature

1. Canfield et al., Science 330: 192-196 (2010).
2. Erisman et al., Nat. Geosci. 1: 636-639 (2008).
3. Steffen et al., Science 347: 1259855 (2015).
4. Daims et al., Nature 528: 504-509 (2015).
5. van Kessel et al., Nature 528: 555-559 (2015).
6. Pjevac et al., Front. Microbiol. 8: 1508 (2016).
7. Kits et al., Nature 549: 269-272 (2017).
8. Daims et al., Trends Microbiol. 24: 699-712 (2016).