Journal
SOIL BIOLOGY & BIOCHEMISTRY
Volume 41, Issue 6, Pages 1289-1300Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.soilbio.2009.03.015
Keywords
Microbial diversity; Environmental changes; Hydrological flowpaths; Denitrification; Nitrate reducers; narG; T-RFLP
Categories
Funding
- Marais du Cotentin et du Bessin
- General council of the department of the 'Manche'
- Regional council of Normandy
- Water Agency of Seine Normandy
- CNRS'
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Factors influencing nitrate dynamics and nitrate-reducing bacteria in peat soil in the field, were investigated in laboratory experiments. A previous study had indicated that the on-site effects of redox conditions and nutrient fluxes on microbial activity were influenced by hydrological conditions. However, the laboratory experiments indicated that peat samples from sites under different hydrological regimes exhibited different microbial activities independently of oxygenation conditions. The effects of redox conditions and nutrient fluxes (i.e. influence of NO3- and O-2 concentration) on the nitrate reducer community were therefore assessed. Microbial community structures in peat samples from sites under different hydrologic regimes were compared using Terminal-Restriction Fragment Length Polymorphism diversity signatures of the narG gene. This gene encodes the catalytic subunit of the nitrate reductase. Unexpectedly, the nitrate reducer communities were very similar at the beginning of the experiment whatever the peatland soil analysed. However, a strong structuration and divergence within the nitrate reducer communities, that was site-dependent, was evident after 76 h of incubation. These modifications within the microbial communities seemed to be due to differences in peat saturation at the sampling sites resulting from the different hydrological regimes. Of the forcing variables tested, oxygenation had a slight effect on the composition of the nitrate-reducers' community whereas nitrate addition had no effect. This study shows that a physical constraint such as hydrological regime might be considered important in microbial community composition. (C) 2009 Elsevier Ltd. All rights reserved.
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