Projects
Coastal microbial mats are among the most productive ecosystems on earth and play a major role in both the carbon and the nitrogen cycle. The typical structure of microbial mats is built by different functional groups of microorganisms including nitrogen fixers; among which cyanobacteria play a key role. Biological nitrogen fixation is the only process compensating for the loss of nitrogen gasses via denitrification. Nitrogenase, the enzyme catalyzing the reduction of N
2 to 2NH
3, is only found in prokaryotic microorganisms.
The project aims to assess the function and diversity of nitrogen fixing microorganisms in coastal microbial mats and to identify the niches of these organisms. Furthermore, the controlling environmental factors of nitrogen fixation at the ecosystem level ought to be determined.
This will be achieved by applying various methods including molecular approaches, like the construction of nifH clone libraries and quantitative RT-PCR to assess nifH gene expression, as well as near real time monitoring of nitrogenase activity using laser-based photoacoustic ethylene detection. Both nitrogenase activity and nifH gene expression will be measured under different laboratory and environmental conditions to reveal natural patterns of nitrogen fixation as well as the response to changing environmental conditions.
Selected Publications
Severin, I. and Stal, L. J. (2008) Light dependency of nitrogen fixation in a coastal microbial mat. ISME J. 2: 1077-1088.
