AUTHOR=Mand Jaspreet , Park Hyung Soo , Jack Thomas R. , Voordouw Gerrit 

TITLE=The role of acetogens in microbially influenced corrosion of steel

JOURNAL=Frontiers in Microbiology

VOLUME=5

YEAR=2014

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2014.00268

DOI=10.3389/fmicb.2014.00268

ISSN=1664-302X

ABSTRACT=<p>Microbially influenced corrosion (MIC) of iron (Fe<sup>0</sup>) by sulfate-reducing bacteria (SRB) has been studied extensively. Through a mechanism, that is still poorly understood, electrons or hydrogen (H<sub>2</sub>) molecules are removed from the metal surface and used as electron donor for sulfate reduction. The resulting ferrous ions precipitate in part with the sulfide produced, forming characteristic black iron sulfide. Hydrogenotrophic methanogens can also contribute to MIC. Incubation of pipeline water samples, containing bicarbonate and some sulfate, in serum bottles with steel coupons and a headspace of 10% (vol/vol) CO<sub>2</sub> and 90% N<sub>2</sub>, indicated formation of acetate and methane. Incubation of these samples in serum bottles, containing medium with coupons and bicarbonate but no sulfate, also indicated that formation of acetate preceded the formation of methane. Microbial community analyses of these enrichments indicated the presence of <italic>Acetobacterium</italic>, as well as of hydrogenotrophic and acetotrophic methanogens. The formation of acetate by homoacetogens, such as <italic>Acetobacterium woodii</italic> from H<sub>2</sub> (or Fe<sup>0</sup>) and CO<sub>2</sub>, is potentially important, because acetate is a required carbon source for many SRB growing with H<sub>2</sub> and sulfate. A consortium of the SRB <italic>Desulfovibrio vulgaris</italic> Hildenborough and <italic>A. woodii</italic> was able to grow in defined medium with H<sub>2</sub>, CO<sub>2</sub>, and sulfate, because <italic>A. woodii</italic> provides the acetate, needed by <italic>D. vulgaris</italic> under these conditions. Likewise, general corrosion rates of metal coupons incubated with <italic>D. vulgaris</italic> in the presence of acetate or in the presence of <italic>A. woodii</italic> were higher than in the absence of acetate or <italic>A. woodii</italic>, respectively. An extended MIC model capturing these results is presented.</p>