ACTIVITY, MICROENVIRONMENTS, AND COMMUNITY STRUCTURE OF AEROBIC AND ANAEROBIC AMMONIUM OXIDIZING PROKARYOTES IN ESTUARINE SEDIMENT (RANDERS FJORD, DK) A. Schramm 1, N.P. Revsbech 1, T. Dalsgaard 2, E. Piña-Ochoa 3, J. de la Torré 4, D.A. Stahl 4, N. Risgaard-Petersen 2 1 Department of Biological Sciences, Microbiology, University of Aarhus, Aarhus, Denmark; 2 National Environmental Research Institute, Silkeborg, Denmark; 3 Centro De Ciencias Medioambientales (CSIC), Madrid; 4 Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, USA Anammox, the anaerobic conversion of ammonium with nitrite to N2, is increasingly recognized as link in the aquatic nitrogen cycle. However, factors regulating the occurrence and activity of anammox bacteria are still poorly understood. Besides the influence of abiotic factors, anammox might be controlled by either aerobic ammonia oxidizing bacteria and archaea (AOB and AOA) or nitrate-reducing/denitrifying bacteria via their supply of nitrite. Along the Randers Fjord estuary (Denmark), gradients of salinity, nutrients, and organic loading can be observed, and anammox has been detected previously at some sites. The aim of this study was to correlate the activity, abundance, and diversity of anammox bacteria, AOB and AOA in surface sediment along the fjord with the sediment microdistribution of nitrite. Using 15N incubations, 16S rRNA gene sequencing, and fluorescence in situ hybridization, anammox was only detected at the two innermost stations where it accounted for 5-16% of the total N2 production and 0.1-0.25% of the total prokaryotic population. These numbers result in cell-specific anammox rates of about 6 fmol N day-1, comparable to literature values. Anammox cells occurred mainly in clusters and were related to the candidate genus Scalindua. Based on ammonia monoxygenase (amoA) gene sequencing, AOB were affiliated with uncultured AOB commonly found in other estuarine sediments; in addition, AOA related to the recently described crenarchaeal ammonia oxidizer Nitrosopumilus maritimus could be detected. However, nitrite microprofiles showed no direct nitrite transfer from AOB and AOA to anammox; instead, anammox seem to depend on suboxic nitrite produced by nitrate reduction.
Hidden Powers - Microbial Communities in Action. Proceedings of the 11th International Symposium on Microbial Ecology (isme-11), 2006
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11th International Symposium on Microbial Ecology (ISME-11), 2006