Shewanella oneidensis MR-1 accelerates the corrosion of carbon steel using multiple electron transfer mechanisms

Abstract

Despite increasing interest in corrosion caused by direct electron transfer (DET) from steel surfaces to microbial cells, the validity of this mechanism is debated. This is often because of the inability to differentiate between the extent of corrosion due to DET and the microbial consumption of H2. Shewanella oneidensis is linked to corrosion of steel and capable of engaging in extracellular electron transfer and consuming H2. However, it is not clear how S. oneidensis corrodes steel. We tested the ability of S. oneidensis to corrode carbon steel through a DET mechanism independently from its H2-consuming capabilities by performing anaerobic corrosion experiments of carbon steel with an S. oneidensis strain incapable of consuming H2 (ΔhydAΔhyaB) and a strain unable to engage in DET (ΔMtr). We found that S. oneidensis accelerates the steel corrosion rate by up to four times relative to an abiotic control and corrosion is coupled to the reduction of fumarate to succinate. More localized corrosion and higher cell density on the steel surface is observed when cells are restricted to DET alone than when only H2 consumption is operational. Coupon weight loss and Linear Polarization Resistance measurements show that the wild-type strain preferentially used the DET mechanism to corrode steel under anoxic conditions. This study illustrates the use of mutant strains as an experimental approach to distinguish DET from H2-mediated electron transfer.