Theme 1
Project 1051

Ecophysiology and role of marine crenarchaeota in the present day marine N cycle
Project leader: Prof. dr. ir. M. S. M. Jetten
Researcher(s): Dr. S. C. M. Haaijer
Starting date: 1-jan-07

Until a decade 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 to what extent the different groups contribute to the (marine) N cycle. This project will continue with the successful enrichment of marine Crenarchaeota capable of nitrification in the North Sea. These enrichments will be the basis for further isolation in dilution series and continuous cultivation under defined environmental conditions (oxygen, ammonia, temperature). The isolated Crearchaeota will be compared to Candidatus “Nitrosopumilus maritimus” in physiological experiments (nitrification rates, influence of NOx; oxygen range) under the same defined conditions. Relevant gene sequences of the isolated micro-organisms will be determined (16S rRNA, amoA- hao,- nirK,- and norB-genes). Finally, we will determine the ‘natural’ partners of the Crenarchaeota for nitrite reduction of nitrite oxidation in environmental samples using molecular and isotopic methods.

Haaijer, S.C.M., Lamers, L.P.M., Smolders, A.J.P., Jetten, M.S.M., Op de Camp, H.J.M., 2007 (2007). Iron sulfide and pyrite as potential electron donors for microbial nitrate reduction in freshwater wetlands . Geomicrobiology Journal24 (5): 391-401.
Darwin Center authors: op den Camp H. J. M., Haaijer S. C. M., Jetten M. S. M.

Haaijer, S.C.M., Harhangi, H.R., Meijerink, B.B., Strous, M., Pol, A., Smolders, A.J.P., Verwegen, K., (...), Op Den Camp, H.J.M. (2008). Bacteria associated with iron seeps in a sulfur-rich, neutral pH, freshwater ecosystem . ISME2 (12): 1231-1242.
Darwin Center authors: op den Camp H. J. M., Haaijer S. C. M.

Jia Yan, Op den Camp, H.J.M., Jetten, M.S.M., Yong Y. Hu, and Haaijer, S.C.M. (2010). Induced cooperation between marine nitrifiers and anaerobic ammonium-oxidizing bacteria by incremental exposure to oxygen. Systematic and Applied Microbiologydoi:10.1016/j.syapm.2010.08.003:
Darwin Center authors: op den Camp H. J. M., Haaijer S. C. M., Jetten M. S. M.