1. Department
of Earth Sciences - Geochemistry, Faculty of Geosciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands
2. Department
of Microbiology, Institute for Water and Wetland Research, Faculty
of Science, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands
3. Institute
for Marine and Atmospheric Research Utrecht (IMAU), Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
4. Laboratoire
de Glaciologie, Université Libre de Bruxelles, 50 Avenue
F. D. Roosevelt, B-1050 Bruxelles, Belgium
5. Department
of Biochemistry and Microbiology, Laboratory of Microbiology, Ghent University, K. L. Ledeganckstraat 35, 9000 Gent, Belgium