Biology of complete ammonia oxidizers (comammox)
We contributed to the discovery of complete ammonia oxidizers (comammox), which belong to the highly diverse and environmentally widespread genus Nitrospira. In contrast to all other nitrifiers, comammox are capable of complete nitrification (oxidation of ammonia to nitrate) in a single organism. This discovery resolved a century-old question about the nitrogen cycle and fundamentally changed our picture of nitrification. It also raised a large number of new questions ranging from the environmental distribution, ecological niche, and evolution of comammox to the kinetics, regulation, and biochemistry of complete nitrification. Intriguingly, comammox Nitrospira are well adapted to life in oligotrophic habitats: based on their kinetic properties, comammox can outcompete other ammonia oxidizers (including many ammonia-oxidizing archaea) under strong ammonia limitation. We study the biology of these organisms with our primary comammox culture (Nitrospira inopinata), new comammox enrichments, and cultivation-independent approaches in collaboration with the group of Michael Wagner.
Recent project: The Comammox Research Platform
In the Comammox Research Platform, we 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 are structurally and biochemically characterized. How does complete nitrification work in a single organism? What are physiological differences between comammox and canonical nitrifying microbes? Our aim is to obtain an encompassing picture of comammox bacteria across different scales, ranging from details of their unique molecular machinery to their roles within microbial communities and ecosystems. The Comammox Research Platform is a joint initiative of members of the Centre for Microbiology and Environmental Systems Science and the Centre for Molecular Biology at the University of Vienna. The platform was established by the Rectorate of the University of Vienna and was launched in June 2018.
Collaboration partners: Kristina Djinovic-Carugo (University of Vienna & EMBL Grenoble), Leonid Sazanov (Institute of Science and Technology Austria)
Website of The Comammox Research Platform
Selected publications on this topic:
- Daebeler A, Güell-Bujons Q, Mooshammer M, Zechmeister T, Herbold CW, Richter A, Wagner M, Daims H. 2023. Rapid nitrification involving comammox and canonical Nitrospira at extreme pH in saline-alkaline lakes. Environ. Microbiol. 25:1055-1067 https://doi.org/10.1111/1462-2920.16337
- Liu S, Jung MY, Zhang S, Wagner M, Daims H, Wanek W. 2021. Nitrogen kinetic isotope effects of nitrification by the complete ammonia oxidizer Nitrospira inopinata. mSphere 6: e0063421 https://doi.org/10.1128/msphere.00634-21
- Kits KD, Jung M-Y, Vierheilig J, Pjevac P, Sedlacek CJ, Liu S, Herbold CW, Stein LY, Richter A, Wissel H, Brüggemann N, Wagner M, Daims H. 2019. Low yield and abiotic origin of N2O formed by the complete nitrifier Nitrospira inopinata. Nat. Commun. 10:1836 https://doi.org/10.1038/s41467-019-09790-x
- Kits KD, Sedlacek CJ, Lebedeva EV, Han P, Bulaev A, Pjevac P, Daebeler A, Romano S, Albertsen M, Stein LY, Daims H, Wagner M. 2017. Kinetic analysis of a complete nitrifier reveals an oligotrophic lifestyle. Nature 549:269-272 https://doi.org/10.1038/nature23679
- Daims H, Lebedeva EV, Pjevac P, Han P, Herbold C, Albertsen M, Jehmlich N, Palatinszky M, Vierheilig J, Bulaev A, Kirkegaard RH, von Bergen M, Rattei T, Bendinger B, Nielsen PH, Wagner M. 2015. Complete nitrification by Nitrospira bacteria. Nature 528: 504-509 https://doi.org/10.1038/nature16461