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Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate-to-ammonium reducers

Helen Decleyre (UGent) , Kim Heylen (UGent) , Carl Van Colen (UGent) and Anne Willems (UGent)
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Abstract
The estuarine nitrogen cycle can be substantially altered due to anthropogenic activities resulting in increased amounts of inorganic nitrogen (mainly nitrate). In the past, denitrification was considered to be the main ecosystem process removing reactive nitrogen from the estuarine ecosystem. However, recent reports on the contribution of dissimilatory nitrate reduction to ammonium (DNRA) to nitrogen removal in these systems indicated a similar or higher importance, although the ratio between both processes remains ambiguous. Compared to denitrification, DNRA has been underexplored for the last decades and the key organisms carrying out the process in marine environments are largely unknown. Hence, as a first step to better understand the interplay between denitrification, DNRA and reduction of nitrate to nitrite in estuarine sediments, nitrogen reduction potentials were determined in sediments of the Paulina polder mudflat (Westerschelde estuary). We observed high variability in dominant nitrogen removing processes over a short distance (1.6m) with nitrous oxide, ammonium and nitrite production rates differing significantly between all sampling sites. Denitrification occurred at all sites, DNRA was either the dominant process (two out of five sites) or absent, while nitrate reduction to nitrite was observed in most sites but never dominant. In addition, novel nitrate-to-ammonium reducers assigned to Thalassospira, Celenbacter, and Halomonas, for which DNRA was thus far unreported, were isolated, with DNRA phenotype reconfirmed through nrfA gene amplification. This study demonstrates high small scale heterogeneity among dissimilatory nitrate reduction processes in estuarine sediments and provides novel marine DNRA organisms that represent valuable alternatives to the current model organisms.
Keywords
LOIHICA STRAIN PV-4, intertidal sediments, NITRITE REDUCTASE, ESCHERICHIA-COLI, DESULFOVIBRIO-DESULFURICANS, ENVIRONMENTAL CONTROLS, ACETYLENE INHIBITION, BACILLUS-SUBTILIS, marine environment, isolation, ammonification, nitrate reducers, MARINE SEDIMENT, RIVER ESTUARY, SHORT-CIRCUIT

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Chicago
Decleyre, Helen, Kim Heylen, Carl Van Colen, and Anne Willems. 2015. “Dissimilatory Nitrogen Reduction in Intertidal Sediments of a Temperate Estuary: Small Scale Heterogeneity and Novel Nitrate-to-ammonium Reducers.” Frontiers in Microbiology 6.
APA
Decleyre, H., Heylen, K., Van Colen, C., & Willems, A. (2015). Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate-to-ammonium reducers. FRONTIERS IN MICROBIOLOGY, 6.
Vancouver
1.
Decleyre H, Heylen K, Van Colen C, Willems A. Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate-to-ammonium reducers. FRONTIERS IN MICROBIOLOGY. 2015;6.
MLA
Decleyre, Helen, Kim Heylen, Carl Van Colen, et al. “Dissimilatory Nitrogen Reduction in Intertidal Sediments of a Temperate Estuary: Small Scale Heterogeneity and Novel Nitrate-to-ammonium Reducers.” FRONTIERS IN MICROBIOLOGY 6 (2015): n. pag. Print.
@article{7010242,
  abstract     = {The estuarine nitrogen cycle can be substantially altered due to anthropogenic activities resulting in increased amounts of inorganic nitrogen (mainly nitrate). In the past, denitrification was considered to be the main ecosystem process removing reactive nitrogen from the estuarine ecosystem. However, recent reports on the contribution of dissimilatory nitrate reduction to ammonium (DNRA) to nitrogen removal in these systems indicated a similar or higher importance, although the ratio between both processes remains ambiguous. Compared to denitrification, DNRA has been underexplored for the last decades and the key organisms carrying out the process in marine environments are largely unknown. Hence, as a first step to better understand the interplay between denitrification, DNRA and reduction of nitrate to nitrite in estuarine sediments, nitrogen reduction potentials were determined in sediments of the Paulina polder mudflat (Westerschelde estuary). We observed high variability in dominant nitrogen removing processes over a short distance (1.6m) with nitrous oxide, ammonium and nitrite production rates differing significantly between all sampling sites. Denitrification occurred at all sites, DNRA was either the dominant process (two out of five sites) or absent, while nitrate reduction to nitrite was observed in most sites but never dominant. In addition, novel nitrate-to-ammonium reducers assigned to Thalassospira, Celenbacter, and Halomonas, for which DNRA was thus far unreported, were isolated, with DNRA phenotype reconfirmed through nrfA gene amplification. This study demonstrates high small scale heterogeneity among dissimilatory nitrate reduction processes in estuarine sediments and provides novel marine DNRA organisms that represent valuable alternatives to the current model organisms.},
  articleno    = {1124},
  author       = {Decleyre, Helen and Heylen, Kim and Van Colen, Carl and Willems, Anne},
  issn         = {1664-302X},
  journal      = {FRONTIERS IN MICROBIOLOGY},
  keyword      = {LOIHICA STRAIN PV-4,intertidal sediments,NITRITE REDUCTASE,ESCHERICHIA-COLI,DESULFOVIBRIO-DESULFURICANS,ENVIRONMENTAL CONTROLS,ACETYLENE INHIBITION,BACILLUS-SUBTILIS,marine environment,isolation,ammonification,nitrate reducers,MARINE SEDIMENT,RIVER ESTUARY,SHORT-CIRCUIT},
  language     = {eng},
  pages        = {12},
  title        = {Dissimilatory nitrogen reduction in intertidal sediments of a temperate estuary: small scale heterogeneity and novel nitrate-to-ammonium reducers},
  url          = {http://dx.doi.org/10.3389/fmicb.2015.01124},
  volume       = {6},
  year         = {2015},
}

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