Biosynthesized Silver Nanoparticles From Bacillus stercoris 2AT10: Synthesis, Characterization, and Antimicrobial...

Paronychia represents an underexplored clinical condition with limited alternatives to conventional antimicrobial therapies, which are increasingly compromised by antibiotic resistance and toxicity. Here, we report for the first time the extracellular biosynthesis of silver nanoparticles (BAgNPs) using Bacillus stercoris 2AT10, a marine-derived bacterium not previously exploited for nanoparticle production. By integrating green nanotechnology with genome mining approaches, we investigated the molecular basis underlying nanoparticle formation and evaluated the potential of BAgNPs against pathogens associated with paronychia. Physicochemical characterization by ultraviolet-visible (UV-Vis) spectroscopy confirmed the presence of particles, with mean sizes ranging from 47 to 87 nm measured by dynamic light scattering (DLS). Their spherical shape was confirmed by transmission electron microscopy (TEM), whereas Fourier-transform infrared (FTIR) spectroscopy suggested the presence of hydroxyl, amide, and nitrogen-containing groups possibly associated with reducing or capping action. Genes encoding nitrate reductases, laccases, and bioactive secondary metabolites, such as bacillibactin, subtilosin A, bacillaene, bacilysin and fengycin, that may be involved in silver ion reduction and nanoparticle stabilization were identified by genome annotation using eggNOG-mapper and antiSMASH. The biosynthesized AgNPs exhibited potent broad-spectrum antimicrobial activity against paronychia-associated pathogens, notably with inhibition zones of 25.8 mm for Staphylococcus aureus and of 23.2 mm for Pseudomonas aeruginosa. The Hen's Egg Test on the Chorioallantoic Membrane (HET-CAM) assay showed the nonirritating profile of the biosynthesized particles (irritation index ≤ 1), supporting further investigation of their suitability for topical applications, pending additional biocompatibility studies. Collectively, these findings establish B. stercoris-derived BAgNPs as a promising green nanotechnology platform to address the unmet need for safe and effective prophylactic agents against bacteria associated with paronychia, with additional potential as antimicrobial preservatives for dermocosmetic formulations.