Impact of Nitrate on the Structure and Function of Bacterial Biofilm Communities in Pipelines Used for Injection of Seawater into Oil Fields

Abstract

We studied the impact of NO 3 ؊ on the bacterial community composition, diversity, and function in in situ industrial, anaerobic biofilms by combining microsensor profiling, 15 N and 35 S 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. NO 3 ؊ was added to the seawater in an attempt to prevent bacterial H 2 S 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, NO 3 ؊ was mainly reduced to NO 2 ؊ . In biofilms grown in the absence of NO 3 ؊ , redox potentials of <؊450 mV at the metal surface suggested the release of Fe 2؉ . NO 3 ؊ 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 NO 3 ؊ reduction occurred upon subsequent withdrawal of NO 3 ؊ . 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 NO 3 ؊ addition.

Dissimilatory reduction of nitrate in seawater by a Methylophaga strain containing two highly divergent narG sequences

“…The deoxygenation system used methanol in the presence of a catalyst to consume O 2 . Schwermer et al (2008) studied the changes in the bacterial biota in the biofilm that developed in the pipes when nitrate was added. They observed an enrichment of 16S rRNA gene sequences related to Methylophaga spp., which DGGE, denaturing gradient gel electrophoresis.…”

Characterization of Corrosive Bacterial Consortia Isolated from Water in a Cooling Tower

“…Nonetheless, the control of corrosive bacterial fouling can be achieved through the application of effective biocides [26], or nitrate, or nitrite [27][28][29][30]. Environmental regulations and the development of water reservoirs in environmentally sensitive areas have spurred the development of easily degradable "green" Chloride (mg/L) 296…”

Effect of Sodium Bisulfite Injection on the Microbial Community Composition in a Brackish-Water-Transporting Pipeline

“…Although the microbial communities in oil and gas fields have been analyzed extensively (3,5,12,17,21), those inhabiting the walls of pipelines transporting oil, water, or gas are only beginning to be characterized (10,15,18,20,25,26,31). Yet understanding these communities is highly relevant, as they contribute to microbially influenced corrosion (MIC), which, along with other forms of corrosion, can lead to pipeline failure.…”