title: Effects of silver nanoparticles on wastewater biofilms.
abstract: The goal of this research is to understand the potential antibacterial effect of silver nanoparticles (Ag-NPs) on biological wastewater treatment processes. It was found that original wastewater biofilms are highly tolerant to the Ag-NP treatment. With an application of 200 mg Ag/L Ag-NPs, the reduction of biofilm bacteria measured by heterotrophic plate counts was insignificant after 24 h. After the removal of loosely bound extracellular polymeric substances (EPS), the viability of wastewater biofilms was reduced when treated under the same conditions. By contrast, when treated as planktonic pure culture, bacteria isolated from the wastewater biofilms were highly vulnerable to Ag-NPs. With a similar initial cell density, most bacteria died within 1 h with the application of 1 mg Ag/L Ag-NPs. The results obtained here indicate that EPS and microbial community interactions in the biofilms play important roles in controlling the antimicrobial effects of Ag-NPs. In addition, slow growth rates may enhance the tolerance of certain bacteria to Ag-NPs. The effects of Ag-NPs on the entire microbial community in wastewater biofilms were analyzed using polymerase chain reaction-denaturing gradient gel electrophoresis, PCR-DGGE. The studies showed that the microbial susceptibility to Ag-NPs is different for each microorganism. For instance, Thiotrichales is more sensitive to Ag-NPs than other biofilm bacteria.
authors.affiliation: Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 2W2, Canada.
authors.forename: Zhiya
authors.initials: Z
authors.lastname: Sheng
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000327:Adsorption / Q000187:drug effects; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification / Q000648:ultrastructure; D018441:Biofilms / Q000187:drug effects*; D001704:Biopolymers / Q000302:isolation & purification; D015169:Colony Count, Microbial; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000633:toxicity / Q000648:ultrastructure; D008826:Microbial Sensitivity Tests; D010316:Particle Size; D010933:Plankton / Q000187:drug effects; D012834:Silver / Q000494:pharmacology* / Q000633:toxicity; D014865:Waste Disposal, Fluid
chemical_list: D001704:Biopolymers; D012834:Silver