Nitrification
The biological oxidation of ammonia to nitrite and further to nitrate is of fundamental significance for the function of the N-cycle in natural and engineered ecosystems. We are interested in analyzing the diversity of nitrifying microorganisms originating from moderate and extreme environments.
For example, ‘Candidatus Nitrososphaera gargensis’, a moderately thermophilic ammonia oxidizing archaeon from the Garga spring in Siberia was characterized and the complete genome was annotated.
One of our main research fields is the selective enrichment of novel nitrite oxidizers. In 2007, a new cold-adapted betaproteobacterium from permafrost-affected soils in the Siberian Arctic was described as 'Candidatus Nitrotoga arctica'.
During the last decade, Nitrospira turned out to be the most abundant nitrite oxidizing bacterium in waste water treatment plants and geothermal environments. A typical member of hot springs, N. calida , was recently isolated.
In activated sludge, Nitrospira coexists together with Nitrobacter and Nitrotoga. Besides nitrite, temperature was identified as main factor influencing the population structure of nitrite oxidizing bacteria.
In aquaculture, nitrification is performed in biofilters with ammonia and nitrite oxidizers immobilized on carrier elements. We investigate nitrification performance in dependence e.g. on nitrogen load and system variables.
Current projects include:
- Diversity of Nitrospira from extreme and moderate environments
- Nitrifying communities in thermophilic habitats
- Physiological investigations on nitrite oxidizing bacteria inhabiting activated sludge
- Optimization of nitrification in recirculation aquaculture systems
Collaboration partners:
Michael Wagner and Holger Daims, University of Vienna
Elena Lebedeva, Russian Academy of Sciences, Moscow
André Lipski, University of Bonn
Eva-Maria Pfeiffer, Institute of Soil Science, University of Hamburg