A model for anoxic iron corrosion by Sh. oneidensis MR-1 based on cell density related H2 consumption and Fe (II) precipitation

In the absence of oxygen, a protective H2 film is formed around an Fe(0) surface, inhibiting the electron flow from this surface. Our study of anoxic corrosion of Fe(0) beads revealed that, in the presence of Shewanella oneidensis MR-1, H2 removal and precipitation of Fe mineral particles on the cell surface are determining processes for corrosion. These two biologically mediated processes were governed by cell density. Addition of supernatant of a corrosion assay with high cell concentration induced metabolic activity in a corrosion assay with low cell concentration, resulting in increased H2 consumption and Fe release from Fe(0) beads. Homoserine lactone-like molecules were detected in the supernatant by a bio-assay, suggesting the involvement of a quorum-sensing regulatory mechanism. The interaction of Sh. oneidensis MR-1 with mineral particles was further investigated by means of the mutant Sh. oneidensis COAG. The COAG mutant exhibited increased biomineralization (up to https://www.w3.org/1998/Math/MathML" display="inline"> 50 % increase) and the putative interactions between COAG cells and mineral precipitates were validated by means of transcriptional analysis and Proteomics.