Effects of silver nanoparticles on bacterial activity in natural waters

Abstract

Silver nanoparticles (AgNPs) may be introduced into aquatic ecosystems because of their widespread use as antimicrobial agents. However, few studies have investigated the impacts of AgNPs on natural aquatic microbial activity in an environmentally relevant context. In this study, bacterioplankton were collected from nine aquatic habitats and exposed to six concentrations of carboxy-functionalized AgNP (ViveNano, 10-nm particle size, 20% Ag w/w) over 48 h. After 1 h of exposure, bacterial production and extracellular alkaline phosphatase affinity were significantly reduced in all AgNP-exposed samples. However, across a 48-h exposure, extracellular aminopeptidase affinity was not consistently impacted by AgNPs. After 48 h, bacterial production recovered by 40 to 250% at low AgNP nominal concentrations (0.05 and 0.1 mg/L) but remained inhibited at the two highest AgNP nominal concentrations (1 and 10 mg/L). In contrast, AgNO(3) additions between 0.01 to 2 mg Ag/L fully inhibited bacterial production over the 48-h exposure. At 48-h exposure, the lowest observed effective concentrations and average median effective concentration for bacterial production ranged from 8 to 66 and 15 to 276 µg Ag/L, respectively. Thus, in natural aquatic systems, AgNP concentrations in the nanogram per liter range are unlikely to negatively impact aquatic biogeochemical cycles. Instead, exposures in the low microgram per liter range would likely be required to negatively impact natural aquatic bacterioplankton processes.

Impact of TiO2 nanoparticles on freshwater bacteria from three Swedish lakes

“…This relative stimulation by TiO2NP could be based on the removal of competitors from the community; however studies investigating the effects of TiO2NP exposure on bacterial community composition are necessary to understand these mechanisms. Changes in bacterial community structure when exposed to AgNP have been previously reported (Das et al 2012, Doiron et al 2012. A reduction in abundance and number of Operational Taxonomic…”

“…Das and co-workers observed AgNP intolerant, -recovering, -tolerant and -stimulated bacterial groups in their experiment (Das et al 2012). However, they reported a reduction in cellspecific bacterial activity after a 5-day exposure, which is in contrast to our study, showing enhanced activity rates under in situ conditions.…”

Fungicidal and antibacterial activity of the hydrogel compositions with silver

“…For example, the EC50 values of silver ions and nanoparticles for bacterial and fungi microflora in natural water systems and in cultural liquids usually do not exceed 100-200 ppb [10,23,24]. Bactericidal concentrations of silver in water of 10-1000 ppb also are far below dangerous thresholds for humans, according to [23] in contrast with the silver PPAs with the concentrations of tens of ppm.…”

Understanding bioenergy production and optimisation at the nanoscale – a review

“…Das et al [48] reported that nanosilver has significant adverse effects on growth and morphology of these filamentous green algae in a dose-dependent manner. Exposure of algal thalli to increasing concentrations of silver nanoparticles resulted in progressive depletion in algal chlorophyll content, chromosome instability and mitotic disturbance, associated with morphological malformations in algal filaments.…”