Label-Free Proteomic Approach to Study the Non-lethal Effects of Silver Nanoparticles on a Gut Bacterium

Abstract

Among all the food-related nanoparticles consumed every day, silver nanoparticles (AgNPs) have become one of the most commonly utilized because of their antimicrobial properties. Despite their common use, the effects of sublethal concentrations of AgNPs, especially on gut biofilms, have been poorly investigated. To address this issue, we investigated in vitro the proteomic response of a monospecies Escherichia coli gut biofilm to chronic and acute exposures in sublethal concentrations of AgNPs. We used a new gel- and label-free proteomic approach based on shotgun nanoflow liquid chromatography–tandem mass spectrometry. This approach allows a quantification of the whole proteome at a dynamic range that is higher than the traditional proteomic investigation. To assess all different possible exposure scenarios, we compared the biofilm proteome of four treatments: (i) untreated cells for the control treatment, (ii) cells treated with 1 μg/ml AgNPs for 24 h for the acute treatment, (iii) cells grown with 1 μg/ml AgNPs for 96 h for the chronic treatment, and (iv) cells grown in the presence of 1 μg/ml AgNPs for 72 h and then further treated for 24 h with 10 μg/ml AgNPs for the chronic + acute treatment. Among the 1,917 proteins identified, 212 were significantly differentially expressed proteins. Several pathways were altered including biofilm formation, bacterial adhesion, stress response to reactive oxygen species, and glucose utilization.

Molecular Mechanisms of Nanomaterial-Bacterial Interactions Revealed by Omics—The Role of Nanomaterial Effect Level

“…The most often studied ENM type at sub-inhibitory effect levels was Ag, similarly to the studies using inhibitory ENM levels. A novel gel- and label-free proteomic approach was used to explore the effects of sublethal concentrations of Ag NPs on E. coli biofilms as a model for gut bacteria ( Domingo et al, 2019 ). The new method yielded 212 differentially expressed proteins which is approximately a 6 times higher value than the average number of differentially expressed proteins in all the other proteomics studies using sub-inhibitory concentrations of ENMs, suggesting that advanced technologies may benefit omics approaches with increased detection sensitivity.…”

Silver and Hyaluronic Acid-Coated Gold Nanoparticles Modulate the Metabolism of a Model Human Gut Bacterium Lactobacillus casei

“…Previous studies with Gram-positive bacteria have shown that Ag NPs at sub-growth-inhibitory concentrations affect the production of quorum-sensing-related proteins [57]. Sub-lethal levels of Ag NPs have also been shown to affect proteins associated with biofilm formation of Gram-negative bacteria [58], suggesting interference with bacterial signaling and functional compound secretion. While low concentrations of certain types of metal NPs that contain biologically active metals (such as ZnO) can stimulate quorum sensing and biofilm formation via providing additional nutrients [59], Ag NPs as a non-essential metal NP may have a different effect.…”

Analytical methods for assessing antimicrobial activity of nanomaterials in complex media: advances, challenges, and perspectives

“…The results demonstrated that this method could be utilized to monitor bacterial proliferation in real time without interfering with the living organisms. Mass spectrometry was successfully used for AST in a urinary tract infection [ 146 ] and to study the non-lethal effects of Ag nanoparticles on a gut bacterium [ 147 ] by monitoring bacterial growth. It is reasonable to believe that this method will be useful for determining the antimicrobial activity of ENMs including via portable mass spectrometry [ 148 ].…”