Diversity of the nitrite reductase gene nirS in the sediment of a free-water surface constructed wetland Authors Olaya Ruiz-Rueda Institute of Aquatic Ecology, Faculty of Sciences, University of Girona, Girona, Spain Rosalia Trias Institute of Aquatic Ecology, Faculty of Sciences, University of Girona, Girona, Spain Librado J. Garcia-Gil Department of Biology, University of Girona, Girona, Spain Lluís Bañeras Institute of Aquatic Ecology, Faculty of Sciences, University of Girona, Girona, Spain Keywords: nirS gene, denitrification, free water surface constructed wetland, sediments Abstract The diversity of the nitrite reductase gene nirS was studied in the bulk sediment of a free-water surface constructed wetland (FWS-CW) located next to the Empuriabrava wastewater treatment plant (WWTP), in Castelló d’Empúries (Girona, NE Spain). The study period extended from the inception of the treatment wetland, in June 1998, until March 1999 and comprised periods of relatively high nitrate and ammonium concentrations at the influent and low nitrate-removal efficiencies. To evaluate nirS diversity, partial gene sequences were obtained by cloning of the respective PCR products. Rarefaction curves based on DOTUR analyses of the deduced amino-acid sequences predicted a greater diversity of nirS genes in samples containing higher ammonium concentrations. Estimated Shannon-Weaver indices of the four cloned samples showed a positive relationship with the N-NH4 +/N-NO3− ratios measured at the FWS-CW inlet. Identities between the deduced amino-acid sequences and those previously deposited in public databases ranged from 72 to 97%. Phylogenetic analysis based on these deduced sequences grouped 165 nirS clones in seven main clusters according to high similarity indices. Up to 60% of the clones clustered together in a highly homogeneous group with little homologies to any sequence retrieved from cultured representatives. Moreover, prevailing environmental conditions appeared to select for particular denitrifying populations, e.g., with respect to ammonium load and nitrogen removal efficiencies. This observation is of particular interest for the management of treatment wetlands, in which only slight variations in the theoretical denitrification potential of the system can occur. [Int Microbiol 2007; 10(4): 253-260] Author Biographies Olaya Ruiz-Rueda, Institute of Aquatic Ecology, Faculty of Sciences, University of Girona, Girona, Spain Institute of Aquatic Ecology, Faculty of Sciences, University of Girona, Girona, Spain Rosalia Trias, Institute of Aquatic Ecology, Faculty of Sciences, University of Girona, Girona, Spain Institute of Aquatic Ecology, Faculty of Sciences, University of Girona, Girona, Spain Librado J. Garcia-Gil, Department of Biology, University of Girona, Girona, Spain Department of Biology, University of Girona, Girona, Spain Lluís Bañeras, Institute of Aquatic Ecology, Faculty of Sciences, University of Girona, Girona, Spain Institute of Aquatic Ecology, Faculty of Sciences, University of Girona, Girona, Spain Downloads PDF Published 2010-01-21 Issue Vol. 10 No. 4 (2007) Section Research Articles License Submission of a manuscript to International Microbiology implies: that the work described has not been published before, including publication in the World Wide Web (except in the form of an Abstract or as part of a published lecture, review, or thesis); that it is not under consideration for publication elsewhere; that all the coauthors have agreed to its publication. 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