Direct cathodic electron uptake coupled to sulfate reduction by <i>Desulfovibrio ferrophilus</i> <scp>IS5</scp> biofilms
Alexandra L. McCully, Alfred M. Spormann
Abstract
Summary Direct electron uptake is emerging as a key process for electron transfer in anaerobic microbial communities, both between species and from extracellular sources, such as zero‐valent iron (Fe 0 ) or cathodic surfaces. In this study, we investigated cathodic electron uptake by Fe 0 ‐corroding Desulfovibrio ferrophilus IS5 and showed that electron uptake is dependent on direct cell contact via a biofilm on the cathode surface rather than through secreted intermediates. Induction of cathodic electron uptake by lactate‐starved D. ferrophilus IS5 cells resulted in the expression of all components necessary for electron uptake; however, protein synthesis was required for full biofilm formation. Notably, proteinase K treatment uncoupled electron uptake from biofilm formation, likely through proteolytic degradation of proteinaceous components of the electron uptake machinery. We also showed that cathodic electron uptake is dependent on SO 4 2− reduction. The insensitivity of Fe 0 corrosion to proteinase K treatment suggests that electron uptake from a cathode might involve different mechanism(s) than those involved in Fe 0 corrosion.