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Appl. Environ. Microbiol., Mar 1997, 931-937, Vol 63, No. 3
JW Nijburg, MJL Coolen, S Gerards, PJAK Gunnewiek and HJ Laanbroek
The effects of nitrate availability and the presence of Glyceria maxima on
the composition and activity of the dissimilatory nitrate-reducing
bacterial community were studied in the laboratory. Four different
concentrations of NO(inf3)(sup-), 0, 533, 1434, and 2,905 (mu)g of
NO(inf3)(sup-)-N g of dry sediment(sup-1), were added to pots containing
freshwater sediment, and the pots were then incubated for a period of 69
days. Upon harvest, NH(inf4)(sup+) was not detectable in sediment that
received 0 or 533 (mu)g of NO(inf3)(sup-)-N g of dry sediment(sup-1).
Nitrate concentrations in these pots ranged from 0 to 8 (mu)g of
NO(inf3)(sup-)-N g of dry sediment(sup-1) at harvest. In pots that received
1,434 or 2,905 (mu)g of NO(inf3)(sup-)-N g of dry sediment(sup-1), final
concentrations varied between 10 and 48 (mu)g of NH(inf4)(sup+)-N g of dry
sediment(sup-1) and between 200 and 1,600 (mu)g of NO(inf3)(sup-)-N g of
dry sediment(sup-1), respectively. Higher input levels of NO(inf3)(sup-)
resulted in increased numbers of potential nitrate-reducing bacteria and
higher potential nitrate-reducing activity in the rhizosphere. In sediment
samples from the rhizosphere, the contribution of denitrification to the
potential nitrate-reducing capacity varied from 8% under
NO(inf3)(sup-)-limiting conditions to 58% when NO(inf3)(sup-) was in ample
supply. In bulk sediment with excess NO(inf3)(sup-), this percentage was
44%. The nitrate-reducing community consisted almost entirely of
NO(inf2)(sup-)-accumulating or NH(inf4)(sup+)-producing gram-positive
species when NO(inf3)(sup-) was not added to the sediment. The addition of
NO(inf3)(sup-) resulted in an increase of denitrifying Pseudomonas and
Moraxella strains. The factor controlling the composition of the
nitrate-reducing community when NO(inf3)(sup-) is limited is the presence
of G. maxima. In sediment with excess NO(inf3)(sup-), nitrate availability
determines the composition of the nitrate-reducing community.
Copyright © 1997, American Society for Microbiology
Effects of Nitrate Availability and the Presence of Glyceria maxima on the Composition and Activity of the Dissimilatory Nitrate-Reducing Bacterial Community
Department of Plant-Microorganism Interactions, Centre for Terrestrial Ecology, and Department of Microbial Ecology, Centre for Limnology, Netherlands Institute of Ecology, 6666 ZG Heteren, The Netherlands
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