Theme 1 & 2
Project 1111

Elucidating the metabolism of marine anaerobic ammonium oxidizing (anammox) bacteria to understand their role in the biogeochemical cycling of nitrogen
Project leader: Prof. dr. ir. M. S. M. Jetten
Researcher(s): Dr. W. J. Maalcke
Starting date: 15-feb-08

Until 10 years ago, microbiologists assumed that all the major groups of N cycle bacteria were known. However, in recent years spectacular discoveries, such as anammox (anaerobic ammonium oxidation) and crenarchaeotal nitrification, have shown the contrary: We hardly know which micro-organisms are responsible for the major nitrogen conversions, and we know very little how and to what extent the different groups contribute to the (marine) N cycle. This project will continue with the successful enrichment of marine anammox bacteria to explore the potential metabolic traits and pathways of these bacteria. These enrichments will be the basis for continuous cultivation under defined environmental conditions (oxygen exposure, ammonia limitation, organic acid addition, exposure to Mn(IV), and exposure to different temperatures). Samples of the cultures will be analysed at NIOZ for lipid and hopanoid composition. In Nijmegen, both gene expression and proteomics of important anammox genes and proteins will be studied on the same samples to correlate lipid composition to metabolic changes. During a 2009 expedition, the importance of present day anammox in the Arabian Sea which contains the largest oxygen minimum zone in the world will be investigated using the molecular and lipid biomarkers.

Kartal, B., Maalcke, W.J., De Almeida, N.M., Cirpus, I., Gloerich, J., Geerts, W., Op Den Camp, H.J.M., Harhangi, H.R., Janssen-Megens, E.M., Francoijs, K.-J., Stunnenberg, H.G., Keltjens, J.T., Jetten, M.S.M., Strous, M. (2011). Molecular mechanism of anaerobic ammonium oxidation. NatureVolume 479, Issue 7371: 127-130.
Darwin Center authors: op den Camp H. J. M., Jetten M. S. M., Keltjens J. T. M., Maalcke W. J.

De Almeida, N.M. , Maalcke, W.J., Keltjens, J.T., Jetten, M.S.M., Kartal, B (2011). Proteins and protein complexes involved in the biochemical reactions of anaerobic ammonium-oxidizing bacteria . Biochemical Society TransactionsVolume 39, Issue 1: 303-308.
Darwin Center authors: Jetten M. S. M., Keltjens J. T. M., Maalcke W. J.

Wouter Maalcke (2012). Multiheme protein complexes of anaerobic ammonium-oxidizing bacteria.
Darwin Center authors: Maalcke W. J.

Wouter J. Maalcke, Andreas Dietl, Sophie J. Marritt, Julea N. Butt, Mike S. M. Jetten, Jan T. Keltjens, Thomas R. M. Barends, Boran Kartal (2013). Structural basis of biological NO generation by octaheme oxidoreductases. The journal of biological chemistry
Darwin Center authors: Jetten M. S. M., Keltjens J. T. M., Maalcke W. J.