Synchrotron macro ATR-FTIR micro-spectroscopy to unlock silver ion-induced biochemical alterations in bacteria

Bacterial infections are recognized as the leading cause of death for millions of individuals worldwide. There has been a growing research focused on antimicrobial materials that can provide alternatives to antibiotics. Among these, silver has emerged as a promising antibacterial agent, owing to its remarkable antimicrobial properties. However, the antimicrobial mechanisms of silver ions are still being debated. This study aimed to investigate biochemical and morphological changes that occur in two prevalent pathogenic bacterial cell types following treatment with silver ions. Using synchrotron macro-attenuated total reflection-Fourier transform infrared (ATR-FTIR) micro-spectroscopy and high-resolution microscopy, significant alterations in the protein (amide I and amide II) and phospholipid structural components of both bacterial species after silver treatment could be observed. More subtle modifications of Staphylococcus aureus were observed in the polysaccharide and nucleic acid regions than Pseudomonas aeruginosa. These structural variations can be attributed to the potent chemical interactions between silver ions and the thick cell wall of S. aureus. The findings of this research shed light on the antibacterial mechanisms induced by silver ions, offering a fresh perspective through the utilization of synchrotron ATR-FTIR for the identification of these mechanisms. This study contributes to our understanding of the applications of silver ions in combating infections and provides a foundation for further investigations towards developing more effective antibacterial agents and treatments.