Gene-driven regulation of biocorrosion on lightweight magnesium alloy AM60

Current microbiologically influenced corrosion (MIC) research primarily focuses on single bacterial behavior, while studies involving mixed bacterial communities remain limited, particularly on magnesium (Mg) alloys, which are highly susceptible to corrosion in marine environments. It remains unclear how different types of bacteria interact on a Mg alloy surface. In this study, the corrosion behavior of AM60 Mg alloy under the coupled effect of sulfate reducing bacteria (SRB) and nitrate reducing bacteria (NRB) was systematically investigated. Interestingly, SRB consistently accelerated the corrosion damage, while NRB offered limited corrosion mitigation in the first 7 days of immersion. The expression level of the dsrB gene indicating the sulfate reduction capacity inside SRB cells after Mg2 + stimulation increased approximately 200 times compared to the reference sample. This implied that a substantial amount of HS-could be produced by sessile SRB cells on the Mg alloy surface, resulting in severe localized corrosion penetration. The sessile NRB cells could form a relatively uniform and low-porosity biofilm to act synergistically with the native oxide/hydroxide layers on the alloy to partially protect the substrate from corrosion. When NRB was introduced into SRB-containing artificial seawater, NRB mainly inhibited the number of the attached SRB cells through the biological competition effect, thereby alleviating the SRB induced corrosion. Additionally, the narG gene, which could reduce NO3-to NO2-, inside NRB cells might not only suppressed the expression of the dsrB gene inside SRB cells, but also chemically oxidized the HS-produced by SRB, thus also inhibiting the SRB corrosion.