This release is available in German.
The anaerobic oxidation of ammonia (anammox) is an important pathway in the nitrogen cycle that was only discovered in the 1980s. Currently, scientists estimate that about 50 percent of the nitrogen in the atmosphere is forged by this process. A group of specialized bacteria perform the anammox reaction, but so far scientists have been in the dark about how these bacteria could convert ammonia to nitrogen in the complete absence of oxygen. Now, 25 years after its discovery, they finally solved the molecular mechanism of anammox.
Anammox bacteria are very unusual because they contain an organelle which is a typical eukaryotic feature. Inside this organelle, known as the "anammoxosome", the bacteria perform the anammox reaction. The membrane of the anammoxosome presumably protects the cells from highly reactive intermediates of the anammox reaction. These intermediates could be hydrazine and hydroxylamine, as microbiologists proposed many years ago. This was very exciting news because the turnover of hydrazine, a very powerful reductant also used as rocket fuel, had never been shown in biology. However, these early experiments were provisional and many open questions remained.
To finally unravel the pathway experimentally was a very difficult enterprise. Marc Strous from the Max Planck Institute in Bremen says: "The anammox organisms are difficult to cultivate because they divide only once every two weeks. Therefore we had to develop cultivation approaches suitable for such low growth rates. Even after 20 years of trials, we can still only grow the organisms in bioreactors and not in pure culture." In the present study, the researchers make use of the latest innovation in bioreactor technology for anammox cultivation: the membrane bioreactor. In such bioreactors the anammox organisms grow as suspended cell
|Contact: Marc Strous|