IAS Fellows' Seminar - Modification of Clay Minerals to Increase their Antibacterial Efficiency
Previous work has documented the general antibacterial mechanism of iron containing clays that involves hydroxyl radical (•OH) production from soluble Fe2+, and attack of cell membrane and intracellular proteins. Professor Dong has recently explored the role of clay structural Fe(II) in •OH production at near neutral pH and identify a lipid protein involved in the antibacterial process. In-situ imaging revealed damage of a membrane lipid, cardiolipin, in the polar region of E. coli cells, where reactive oxygen species and redox-active labile Fe were enriched. The results advance the previous antibacterial model by demonstrating that the structural Fe(II) is the primary source of •OH, which damages cardiolipin, triggers the influx of soluble Fe2+ into the cell, and ultimately leads to cell death.
In order to improve the efficiency of the antibacterial activity, a direct contact of reduced nontronite (rNAu-2) with negatively bacteria may be required. Professor Dong’s most recent work has focused on the bactericidal properties of a modified clay mineral. This modified nontronite is a more efficient bactericidal agent with a higher lethality at a lower Fe(II) concentration. The slow oxidation of Fe(II) in this modified nontronite contributes to its long-lasting antibacterial effect. He has also investigated how common cations (K, Na, Ca, Mg) influence the bactericidal effect of rNAu-2. Low concentrations of divalent cations (Ca, Mg) dramatically inhibit the toxicity of rNAu-2 to E. coli. The toxicity of rNAu-2 to E. coli decreases with increasing concentration of monovalent cations (Na, K). The protective role of these cations to E. coli may be explained by a biotic ligand model.
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