The uptake, elimination, and toxicity of silver nanoparticles and silver ions in single-species and natural mixed-species bacterial biofilms

• Published in: Journal of water process engineering 2023-12, Vol.56, p.104256, Article 104256
• Main Authors: Li, Nihong, Zhu, Shijun, Wen, Chen, Xu, Hansen, Li, Chunyan, Zhu, Shiqi, Li, Rufei, Chen, Liqiang, Luo, Xia
• Format: Article
• Language: English
• Subjects: Elimination; Mixed biofilm; Silver nanoparticles; Sorption kinetics; Toxicity
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2023.104256

In nature, microorganisms predominantly exist as biofilms, which can reduce the bioavailability of toxic metals in water by adsorbing them. In this study, we investigated the adsorption, elimination, and toxicity of silver nanoparticles (AgNPs) and silver nitrate (AgNO3) in biofilms of the model bacterium Escherichia coli and those composed of natural mixed-species (NMS). Biofilms were exposed to different metal concentrations for 72 h, after which, they were transferred to a clean medium for 7 days to study the elimination of AgNPs and Ag+. We found that pseudo-second order kinetics predominated, and adsorption was jointly governed by external mass transfer and intraparticle diffusion. NMS biofilms were much more tolerant to AgNPs and Ag+ than E. coli biofilms, and Ag+ was much more toxic to both the biofilms than AgNPs. The concentrations of proteins, polysaccharides, and internal metabolites like respiratory chain dehydrogenase and cyclic diguanosine monophosphate were 0.3 to 3.7 fold greater in NMS biofilms than in E. coli biofilms, while those of reactive oxygen species and lactate dehydrogenase were 0.6 to 1.1 fold lower in NMS biofilms, highlighting a significant advantage that metal-exposed NMS biofilms enjoy in terms of both structure and metabolic function. These findings improve our understanding of the potential environmental risks of engineered nanoparticles and provide new insights into the bioremediation of nanoparticles-contaminated aquatic environments using biofilms. [Display omitted] •Adsorption was governed by both intraparticle diffusion and surface adsorption.•Ag+ exhibited a higher extent of toxicity toward both the biofilms.•Ag induced ROS generation, membrane damage and respiratory chain inactivation.•AgNPs/Ag+ diminished biosynthesis of extracellular polysaccharides.•Natural mixed-species biofilms are much more tolerant to AgNPs and Ag+.