Bacterial Diversity and Succession in the Presence of Steel and Effects on Corrosion

Steel corrosion is an extensive problem worldwide, substantially impacting marine infrastructures. In this study, the influence of steel on bacterial succession and corrosion was investigated by culturing marine water samples with and without steel coupons for 14 days. Compared to abiotic controls, oxygen levels were rapidly depleted in biotic cultures. Fe levels increased in controls compared to biotic cultures, potentially due to anoxic conditions and the incorporation of Fe in the biofilm. Proteobacteria dominated the initial cultures, but over 14 days the number of phylogenetic groups decreased overall in abundance. Taxons that increased in abundance included Clostridiaceae, Fusobacteriaceae, Flavobacteriaceae and Prolixibacteraceae, some members of which can utilise Fe. While initially in low abundance, Arcobacteraceae, Pseudoalteromonadaceae, Rhodobacteraceae and Rhizobiaceae numbers increased over time. Sites 1 and 2 cultures displayed localised deep pitting corrosion on coupon surfaces, consistent with microbial action, with an increase in Bacteroidetes, suggesting this phylum facilitates corrosion. In contrast, Site 3 cultures displayed uniform, superficial corrosion, with Clostridiaceae being the dominating family by Day 14, suggesting corrosion inhibition through biofilm formation. By identifying bacteria associated with corrosion, targeted approaches to corrosion reduction may be developed through identifying significant metabolic pathways by transcriptomics and the application of metabolic inhibitors.