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Changes in Benthic Denitrification, Nitrate Ammonification, and Anammox Process Rates and Nitrate and Nitrite Reductase Gene Abundances along an Estuarine Nutrient Gradient (the Colne Estuary, United Kingdom)

Dong, Liang F and Smith, Cindy J and Papaspyrou, Sokratis and Stott, Andrew and Osborn, A Mark and Nedwell, David B (2009) 'Changes in Benthic Denitrification, Nitrate Ammonification, and Anammox Process Rates and Nitrate and Nitrite Reductase Gene Abundances along an Estuarine Nutrient Gradient (the Colne Estuary, United Kingdom).' Applied and Environmental Microbiology, 75 (10). 3171 - 3179. ISSN 0099-2240

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Abstract

<jats:title>ABSTRACT</jats:title> <jats:p> Estuarine sediments are the location for significant bacterial removal of anthropogenically derived inorganic nitrogen, in particular nitrate, from the aquatic environment. In this study, rates of benthic denitrification (DN), dissimilatory nitrate reduction to ammonium (DNRA), and anammox (AN) at three sites along a nitrate concentration gradient in the Colne estuary, United Kingdom, were determined, and the numbers of functional genes ( <jats:italic>narG</jats:italic> , <jats:italic>napA</jats:italic> , <jats:italic>nirS</jats:italic> , and <jats:italic>nrfA</jats:italic> ) and corresponding transcripts encoding enzymes mediating nitrate reduction were determined by reverse transcription-quantitative PCR. In situ rates of DN and DNRA decreased toward the estuary mouth, with the findings from slurry experiments suggesting that the potential for DNRA increased while the DN potential decreased as nitrate concentrations declined. AN was detected only at the estuary head, accounting for ∼30% of N <jats:sub>2</jats:sub> formation, with 16S rRNA genes from anammox-related bacteria also detected only at this site. Numbers of <jats:italic>narG</jats:italic> genes declined along the estuary, while <jats:italic>napA</jats:italic> gene numbers were stable, suggesting that NAP-mediated nitrate reduction remained important at low nitrate concentrations. <jats:italic>nirS</jats:italic> gene numbers (as indicators of DN) also decreased along the estuary, whereas <jats:italic>nrfA</jats:italic> (an indicator for DNRA) was detected only at the two uppermost sites. Similarly, nitrate and nitrite reductase gene transcripts were detected only at the top two sites. A regression analysis of log( <jats:italic>n</jats:italic> + 1) process rate data and log( <jats:italic>n</jats:italic> + 1) mean gene abundances showed significant relationships between DN and <jats:italic>nirS</jats:italic> and between DNRA and <jats:italic>nrfA</jats:italic> . Although these log-log relationships indicate an underlying relationship between the genetic potential for nitrate reduction and the corresponding process activity, fine-scale environmentally induced changes in rates of nitrate reduction are likely to be controlled at cellular and protein levels. </jats:p>

Item Type: Article
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health > Life Sciences, School of
Depositing User: Jim Jamieson
Date Deposited: 23 Sep 2011 09:06
Last Modified: 10 Jun 2021 16:15
URI: http://repository.essex.ac.uk/id/eprint/891

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