title: A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus.
abstract: To investigate the mechanism of inhibition of silver ions on microorganisms, two strains of bacteria, namely Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), were treated with AgNO(3) and studied using combined electron microscopy and X-ray microanalysis. Similar morphological changes occurred in both E. coli and S. aureus cells after Ag(+) treatment. The cytoplasm membrane detached from the cell wall. A remarkable electron-light region appeared in the center of the cells, which contained condensed deoxyribonucleic acid (DNA) molecules. There are many small electron-dense granules either surrounding the cell wall or depositing inside the cells. The existence of elements of silver and sulfur in the electron-dense granules and cytoplasm detected by X-ray microanalysis suggested the antibacterial mechanism of silver: DNA lost its replication ability and the protein became inactivated after Ag(+) treatment. The slighter morphological changes of S. aureus compared with E. coli recommended a defense system of S. aureus against the inhibitory effects of Ag(+) ions.
authors.affiliation: Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Q L
authors.initials: QL
authors.lastname: Feng
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.forename: G Q
authors.initials: GQ
authors.lastname: Chen
authors.forename: F Z
authors.initials: FZ
authors.lastname: Cui
authors.forename: T N
authors.initials: TN
authors.lastname: Kim
authors.forename: J O
authors.initials: JO
authors.lastname: Kim
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000032:analysis / Q000187:drug effects*; D002473:Cell Wall / Q000187:drug effects* / Q000648:ultrastructure; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D004261:DNA Replication / Q000187:drug effects*; D004269:DNA, Bacterial / Q000032:analysis / Q000187:drug effects*; D004577:Electron Probe Microanalysis; D004926:Escherichia coli / Q000737:chemistry / Q000187:drug effects* / Q000648:ultrastructure; D008854:Microscopy, Electron; D012834:Silver / Q000032:analysis; D012835:Silver Nitrate / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000737:chemistry / Q000187:drug effects* / Q000648:ultrastructure; D013455:Sulfur / Q000032:analysis
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D012834:Silver; D013455:Sulfur; D012835:Silver Nitrate