Living commensal biofilms for corrosion prevention

Corrosion imposes a $2.5 trillion annual global cost, with much attributed to microbiologically influenced corrosion (MIC) associated with sulfate-reducing bacteria (SRB). Existing mitigation strategies that rely on biocides or polymeric coatings are costly and ecologically disruptive. Here, we present a four-part framework integrating microbiome engineering, biological passivation, commensal antagonism, and sustainability. We define microbioclaim as a biologically mediated ecological dominance mechanism through which a commensal biofilm establishes protective control over the surface. Using copper (Cu) as a model metal, we show that Citrobacter sp. strain MICI21 forms a commensal biofilm that reduces SRB-induced corrosion in co-culture with Oleidesulfovibrio alaskensis strain G20. MICI21 conferred 3- to 15-fold higher resistance, and multimodal characterization confirmed formation of a compact MICI21-dominated biofilm that resisted sulfide ingress, limited pitting, and exhibited high rigidity (~0.8 GPa). Analyses indicate contributions from Cu–EPS interactions, competitive exclusion of SRB, and a putative Type VI secretion system (T6SS) associated with antagonistic potential in publicly available Citrobacter genomes. Complementary assays using isolated Citrobacter -derived extracellular polymeric substances (EPS), applied to bare copper surfaces in the absence of living cells, showed that EPS alone can contribute to surface passivation in 3.5% NaCl. Together, this work positions microbiome engineering as a design principle for living coatings.