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Applied and Environmental Microbiology, May 2008, p. 2841-2851, Vol. 74, No. 9
0099-2240/08/$08.00+0 doi:10.1128/AEM.02027-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
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Timothy G. Ferdelman,1
Paul Stoodley,3
Armin Gieseke,1 and
Dirk de Beer1
Max Planck Institute for Marine Microbiology, Celsiusstrasse 1, D-28359 Bremen, Germany,1 Oil Plus, Ltd., Kennet Side, Newbury, Berkshire RG14 5PX, United Kingdom,2 Center for Genomic Sciences, Allegheny-Singer Research Institute, 320 East North Avenue, Pittsburgh, Pennsylvania 15212-47723
Received 4 September 2007/ Accepted 3 March 2008
We studied the impact of NO3– on the bacterial community composition, diversity, and function in in situ industrial, anaerobic biofilms by combining microsensor profiling, 15N and 35S labeling, and 16S rRNA gene-based fingerprinting. Biofilms were grown on carbon steel coupons within a system designed to treat seawater for injection into an oil field for pressurized oil recovery. NO3– was added to the seawater in an attempt to prevent bacterial H2S generation and microbially influenced corrosion in the field. Microprofiling of nitrogen compounds and redox potential inside the biofilms showed that the zone of highest metabolic activity was located close to the metal surface, correlating with a high bacterial abundance in this zone. Upon addition, NO3– was mainly reduced to NO2–. In biofilms grown in the absence of NO3–, redox potentials of <–450 mV at the metal surface suggested the release of Fe2+. NO3– addition to previously untreated biofilms induced a decline (65%) in bacterial species richness, with Methylophaga- and Colwellia-related sequences having the highest number of obtained clones in the clone library. In contrast, no changes in community composition and potential NO3– reduction occurred upon subsequent withdrawal of NO3–. Active sulfate reduction was below detection levels in all biofilms, but S isotope fractionation analysis of sulfide deposits suggested that it must have occurred either at low rates or episodically. Scanning electron microscopy revealed that pitting corrosion occurred on all coupons, independent of the treatment. However, uniform corrosion was clearly mitigated by NO3– addition.
Published ahead of print on 14 March 2008.
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Present address: Baker Petrolite, Level 7, 256 St. Georges Terrace, Perth, WA 6000, Australia.
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