Impacts of Silver Nanoparticle Coating on the Nitrification Potential of Nitrosomonas europaea

Abstract

Silver nanoparticles (AgNPs) are increasingly used as bacteriostatic agents to prevent microbial growth. AgNPs are manufactured with a variety of coatings, and their potential impacts on wastewater treatment in general are poorly understood. In the present study, Nitrosomonas europaea, a model ammonia oxidizing bacterium, was exposed to AgNPs with citrate, gum arabic (GA), and polyvinylpyrrolidone (PVP). GA and citrate AgNPs inhibited nitrification most strongly (67.9 ± 3.6% and 91.4 ± 0.2%, respectively at 2 ppm). Our data indicate that Ag(+) dissolution and colloid stability of AgNPs were the main factors in AgNP toxicity. In general, low amounts of dissolved Ag initially caused a post-transcriptional interruption of membrane-bound nitrifying enzyme function, reducing nitrification by 10% or more. A further increase in dissolved Ag resulted in heavy metal stress response (e.g., merA up-regulation) and ultimately led to membrane disruption. The highest effect on membrane disruption was observed for citrate AgNPs (64 ± 11% membranes compromised at 2 ppm), which had high colloidal stability. This study demonstrates that coating plays a very important role in determining Ag dissolution and ultimately toxicity to nitrifiers. More research is needed to characterize these parameters in complex growth media such as wastewater.

Emerging Contaminant or an Old Toxin in Disguise? Silver Nanoparticle Impacts on Ecosystems

“…These results suggest that the water column CO 2 , DOC, and DO concentrations were not the primary drivers of methane concentrations. We therefore speculate that the patterns in methane could have been the result of several different mechanisms: a direct effect of Ag on sensitive membrane bound methane monoxygenase enzymes used by the microbes that metabolize methane; 18 an indirect effect of Ag on methanotrophs mediated by sediment dissolved oxygen and substrate concentrations; or the release of dissolved CH 4 from plant biomass. 40 Through our use of a mixed community of organisms in realistic environmental media and field conditions, our attempt to understand the impacts of nanoparticles on ecosystems led to surprising conclusions.…”

Assessing the Effects of Silver Nanoparticles on Biological Nutrient Removal in Bench-Scale Activated Sludge Sequencing Batch Reactors

“…These concentrations were chosen on the basis of our previous study, which showed that the effects of AgNPs on the model wastewater ammonium oxidizing bacterium (AOB), Nitrosomonas europaea, became apparent around 2 ppm total Ag concentration. 10 Table 1 displays the chronology of Ag addition to the SBRs. Ag was initially added in pulses at 0.2 ppm followed by a continuous addition.…”

The Influential Factors on Antibacterial Behaviour of Copper and Silver Nanoparticles

“…Also, a similar survey has been conducted by Aranout et al [87]. They examined the effect of three types of coatings [gum arabicum (GA), acid citric and PVP] on Table 1.…”