Insights into the various mechanisms by which Shewanella spp. induce and inhibit steel corrosion

Shewanella species are frequently selected as model strains to investigate microbially influenced steel corrosion. This selection is due to their relevance for corrosion, but also because of their easy cultivation in aerobic media. Unfortunately, these cultivation advantages do not lead to a straight-forward interpretation of their corrosion inducing or inhibiting mechanisms. The metabolic versatility of Shewanellae indeed enables a wide variety of corrosion mechanisms. This work reviews the metabolic capacities and the extracellular electron transfer mechanisms of Shewanellae and explains how these abilities lead to the various mechanisms by which Shewanellae induce and inhibit corrosion. It should be emphasized that the medium composition (presence of electron donor, acceptor, carbon source) strongly affects which mechanism is in play. Overall, this work concludes that Shewanellae model strains offer great opportunities to study corrosion, thanks in part due to genetic engineering options, but the full complexity of their corrosion processes should always be kept mind.