Bactericidal potential of silver nanoparticles synthesized using cell-free extract of Comamonas acidovorans: in vitro and in silico approaches

The need to overcome human threats from pathogenic microbes, development of nanomaterials have been provoked for a new generation of antimicrobials. In the present study, biosynthesis of silver nanoparticles (AgNPs) was acquired using Comamonas acidovorans extract within 72 h under static condition. Electron microscopy studies revealed that the size of AgNPs was ranging from 6-53 nm and had spherical, oval and irregular shapes with smooth surfaces. Prepared AgNPs interacted with proteins, carbohydrates and other aromatic molecules. Biosynthesized AgNPs were bactericidal, which significantly inhibited pathogenic microbes, i.e., Streptococcus pyogenes, Staphylococcus aureus and Escherichia coli. Higher concentrations of AgNPs (20 μg ml-1) inhibited 92-98% growth of all tested bacteria within 24 h. AgNPs-protein network studies carried out to recognize the protein interactions with AgNPs and to understand probable bactericidal mechanisms. AgNPs may penetrate into cell through membrane proteins and damage them by modifying amino acids. Due to AgNPs-protein interactions, dysfunctions in enzymes obstruct certain metabolic processes, which cause the bacteria to die eventually. In certain pathogenic microbes, cue and cus systems detoxify Ag+ ions, transport through transporter proteins and expel them to the extracellular space, which are mainly responsible for Ag resistance.