AUTHOR=An Dongshan , Dong Xiaoli , An Annie , Park Hyung S. , Strous Marc , Voordouw Gerrit 

TITLE=Metagenomic Analysis Indicates Epsilonproteobacteria as a Potential Cause of Microbial Corrosion in Pipelines Injected with Bisulfite

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00028

DOI=10.3389/fmicb.2016.00028

ISSN=1664-302X

ABSTRACT=<p>Sodium bisulfite (SBS) is used as an oxygen scavenger to decrease corrosion in pipelines transporting brackish subsurface water used in the production of bitumen by steam-assisted gravity drainage. Sequencing 16S rRNA gene amplicons has indicated that SBS addition increased the fraction of the sulfate-reducing bacteria (SRB) <italic>Desulfomicrobium</italic>, as well as of <italic>Desulfocapsa</italic>, which can also grow by disproportionating sulfite into sulfide, sulfur, and sulfate. SRB use cathodic H<sub>2</sub>, formed by reduction of aqueous protons at the iron surface, or use low potential electrons from iron and aqueous protons directly for sulfate reduction. In order to reveal the effects of SBS treatment in more detail, metagenomic analysis was performed with pipe-associated solids (PAS) scraped from a pipe section upstream (PAS-616P) and downstream (PAS-821TP) of the SBS injection point. A major SBS-induced change in microbial community composition and in affiliated <italic>hynL</italic> genes for the large subunit of [NiFe] hydrogenase was the appearance of sulfur-metabolizing <italic>Epsilonproteobacteria</italic> of the genera <italic>Sulfuricurvum</italic> and <italic>Sulfurovum</italic>. These are chemolithotrophs, which oxidize sulfide or sulfur with O<sub>2</sub> or reduce sulfur with H<sub>2</sub>. Because O<sub>2</sub> was absent, this class likely catalyzed reduction of sulfur (S<sup>0</sup>) originating from the metabolism of bisulfite with cathodic H<sub>2</sub> (or low potential electrons and aqueous protons) originating from the corrosion of steel (Fe<sup>0</sup>). Overall this accelerates reaction of of S<sup>0</sup> and Fe<sup>0</sup> to form FeS, making this class a potentially powerful contributor to microbial corrosion. The PAS-821TP metagenome also had increased fractions of <italic>Deltaproteobacteria</italic> including the SRB <italic>Desulfomicrobium</italic> and <italic>Desulfocapsa</italic>. Altogether, SBS increased the fraction of hydrogen-utilizing <italic>Delta-</italic> and <italic>Epsilonproteobacteria</italic> in brackish-water-transporting pipelines, potentially stimulating anaerobic pipeline corrosion if dosed in excess of the intended oxygen scavenger function.</p>