The involvement of Shewanella spp. in biocorrosion is often attributed to their Fe(III)-reducing properties, but they could also affect corrosion by using metallic iron as an electron donor. Previously, we isolated Shewanella strain 4t3-1-2LB from an acetogenic community enriched with Fe(0) as the sole electron donor. Here, we investigated its use of Fe(0) as an electron donor with fumarate as an electron acceptor and explored its corrosion-enhancing mechanism. Without Fe(0), strain 4t3-1-2LB fermented fumarate to succinate and CO2, as was shown by the reaction stoichiometry and pH. With Fe(0), strain 4t3-1-2LB completely reduced fumarate to succinate and increased the Fe(0) corrosion rate (7.0 ± 0.6)-fold in comparison to that of abiotic controls (based on the succinate-versus-abiotic hydrogen formation rate). Fumarate reduction by strain 4t3- 1-2LB was, at least in part, supported by chemical hydrogen formation on Fe(0). Filtersterilized spent medium increased the hydrogen generation rate only 1.5-fold, and thus extracellular hydrogenase enzymes appear to be insufficient to explain the enhanced corrosion rate. Electrochemical measurements suggested that strain 4t3-1-2LB did not excrete dissolved redox mediators. Exchanging the medium and scanning electron microscopy (SEM) imaging indicated that cells were attached to Fe(0). It is possible that strain 4t3-1-2LB used a direct mechanism to withdraw electrons from Fe(0) or favored chemical hydrogen formation on Fe(0) through maintaining low hydrogen concentrations. In coculture with an Acetobacterium strain, strain 4t3-1-2LB did not enhance acetogenesis from Fe(0). This work describes a strong corrosion enhancement by a Shewanella strain through its use of Fe(0) as an electron donor and provides insights into its corrosion-enhancing mechanism.
Bibliographical noteFunding Information:
J.P. was funded by a postdoctoral grant from the Special Research Fund (BOF) of Ghent University. J.P., A.P., J.B.A.A., and K.R. were supported by the European Research Council via Starter Grant no. 310023 "ELECTROTALK." K.D.P. was supported by the Research Foundation Flanders (SBO BRANDING) and the Special Research Fund (BOF) Concerted Research Actions (GOA, BOF12/GOA/008) from the Flemish Government. In addition, this project was supported by a King Abdullah University of Science & Technology (KAUST) Competitive Research Grant (OSR-2016-CRG5-2985-01). We thank Jana De Bodt (Center for Microbial Ecology and Technology, Ghent University) for her help with sampling. We acknowledge Greet Van de Velde (Center for Microbial Ecology and Technology, Ghent University) for performing the ion chromatography analyses. We thank Pieter Candry and Jo De Vrieze (Center for Microbial Ecology and Technology, Ghent University) for the maintenance of the compact GC. SEM imaging was performed with the appreciated help of Silvia Hidalgo Martinez and Filip Meysman (University of Antwerp). We acknowledge Jeet Varia (Center for Microbial Ecology and Technology, Ghent University) for his useful comments that contributed to this work
© 2018 American Society for Microbiology.
- Extracellular electron transfer mechanisms
- Fumarate fermentation
- Microbially influenced corrosion
- Shewanella fodinae
- Solid electron donors
- Zero-valent iron