Antibacterial Activity and Mechanistic Insights into Bioinspired Hydrophilic Selenium–Iron-Sulfur Hybrid (Se–S–Fe) Nanostructures

Hybrid nanoparticles (HNPs) offer integrated advantages in comparison to the singular-component systems of nanomaterials. This study reports a simple, one-pot green synthesis of hydrophilic selenium-iron-sulfur hybrid nanoparticles (Se-S-Fe HNPs) using an <i>Alstonia scholaris</i> extract. The size and surface charge of the Se-S-Fe HNPs, characterized by advanced material characterization techniques, significantly influenced their antimicrobial activity against <i>Escherichia coli</i> and <i>Bacillus megaterium</i>. However, mechanistic studies uncovered distinct modes of action against these bacterial species. Transcriptomic analysis revealed Se-S-Fe HNPs disrupted protein synthesis in <i>E. coli</i> and elevated the expression of outer membrane proteins OmpA and OmpC. In <i>B. megaterium</i>, the HNPs induced hyperosmotic shock and broad metabolic changes, impacting amino acid biosynthesis and protein localization. This work introduces a facile and environmentally friendly method for producing effective antimicrobial nanomaterials with distinct mechanisms of action depending on bacterial species.