Proteomic Evidence for Biofilm-Mediated Copper Stress Adaptation in Oleidesulfovibrio alaskensis G20.

Copper (Cu) is an essential cofactor for enzymes regulating key metabolic processes; however, excess Cu can inhibit bacterial growth. The ability of Oleidesulfovibrio alaskensis G20 (OA G20) to survive under heavy metal stress is compelling. Our previous study on OA G20 exposed to Cu suggests that bacteria might use biofilm formation to adapt to high levels of toxic metal ions. To elucidate the molecular mechanisms underlying this adaptation, we performed a comparative proteomic analysis of OA G20 stress-induced biofilms (30 μM Cu) versus control (no Cu) and their respective extracellular fractions. Proteomic analysis revealed that among the differentially regulated intracellular proteins identified in this study, 47.93% were upregulated and 52.07% were downregulated in OA G20 biofilms exposed to 30 μM Cu compared to control. Similarly, 41.05% of extracellular proteins were upregulated and 58.95% were downregulated. The significantly modulated proteins (log2FC > 1) were involved in heavy-metal ion transportation, cell division, chemotaxis, cell motility and cell morphology. Our results also identified 133 hypothetical proteins under copper stress, several of which were related to prokaryotic membrane lipoprotein, cell and flagellar motility, and Type VI secretion system, offering new avenues for future research in bioremediation and biofilm mitigation strategies in industrial settings.