Effects of engineered silver nanoparticles on the growth and activity of ecologically important microbes

Abstract

SummaryCurrently, little is known about the impact of silver nanoparticles (AgNPs) on ecologically important microorganisms such as ammonia-oxidizing bacteria (AOB). We performed a multi-analytical approach to demonstrate the effects of uncapped nanosilver (uAgNP), capped nanosilver (cAgNP) and Ag2SO4 on the activities of the AOB: Nitrosomonas europaea, Nitrosospira multiformis and Nitrosococcus oceani, and the growth of Escherichia coli and Bacillus subtilis as model bacterial systems in relation to AgNP type and concentration. All Ag treatments caused significant inhibition to the nitrification potential rates (NPRs) of Nitrosomonas europaea (decreased from 34 to < 16.7 μM NH4 + oxidized day ). Escherichia coli-Ag interactions revealed that the percentage of damaged E. coli cells was 45% greater with Ag2SO4, 39% with cAgNPs and 33% with uAgNPs compared with controls. Generally, the inhibitory effect on AOB NPRs and E. coli/B. subtilis growth was in the following order Ag2SO4 > cAgNP > uAgNP. In conclusion, AgNPs (especially cAgNPs) and Ag2SO4 adversely affected AOB activities and thus have the potential to severely impact key microbially driven processes such as nitrification in the environment.

Estuarine sediment hydrocarbon-degrading microbial communities demonstrate resilience to nanosilver

“…Unlike the cAgNPs, the uAgNPs had no impact on sediment microbial cell counts or the proportion of active cells in the present study, suggesting that the uAgNPs were less toxic than the cAgNPs. Differences in size are likely to have led to differential toxic effects between the cAgNPs and uAgNPs (Beddow et al, 2014). Specifically, the smaller cAgNPs would have increased contact with cell membranes and increased rates of toxic Ag þ dissolution (Sondi and Salopek-Sondi, 2004;Sotiriou et al, 2011;Ma et al, 2012).…”

“…The capped silver nanoparticles (cAgNPs, capped with methoxypolyethylene glycol) were provided as a well-dispersed 0.9 g L À1 suspension of mPEG-coated AgNPs by Dr Paul Christian (University of Manchester, UK). Both nanoparticles have been thoroughly characterized previously (Beddow et al, 2014). The cAgNPs were found to be prominently present as single particles with an average diameter of 17e40 nm (depending on characterization technique) and a zeta potential of À37 mV when dispersed in UHP water, while the uAgNPs tended to form aggregates with an average diameter of 118e188 nm and a zeta potential of À32 mV (Beddow et al, 2014).…”

“…Both nanoparticles have been thoroughly characterized previously (Beddow et al, 2014). The cAgNPs were found to be prominently present as single particles with an average diameter of 17e40 nm (depending on characterization technique) and a zeta potential of À37 mV when dispersed in UHP water, while the uAgNPs tended to form aggregates with an average diameter of 118e188 nm and a zeta potential of À32 mV (Beddow et al, 2014). A 1 g L À1 stock solution of Ag 2 SO 4 (Sigma Aldrich) was used as a source of Ag þ .…”

Release of airborne particles and Ag and Zn compounds from nanotechnology-enabled consumer sprays: Implications for inhalation exposure

“…While the introduction of nanomaterials into consumer products provides various desired or claimed properties, because of their widespread use there is concern regarding the potential environmental and human health effects due to the release of and exposure to nanoparticles (Beddow et al, 2014;Dunphy Guzman et al, 2006;Hansen et al, 2008;Lioy et al, 2010;Majestic et al, 2010;Maynard and Aitken, 2007;McCall, 2011;von Goetz et al, 2013b). Concerns about nanoparticles in consumer products are amplified by studies showing toxicological potential of Ag, ZnO, and TiO2 nanoparticles (Cho et al, 2011;De Jong et al, 2013;Elsaesser and Howard, 2012;Kao et al, 2012;Sung et al, 2008;Warheit et al, 2009;Zhang et al, 2014).…”

Antibacterial activity of gold nanorods against <em>Staphylococcus aureus</em> and<em> Propionibacterium acnes</em>: misinterpretations and artifacts

“…Bacterial growth media (for in vitro studies) are rich in peptides, amino acids, electrolytes, and other chemicals, which may induce aggregation of nanoparticles. Despite the increasing interest in understanding the fate of nanomaterials in biological media, [19][20][21] to the best of our knowledge, no systematic investigations on the colloidal stability of GNR when mixed with bacterial growth media were conducted in the literature. Ignoring such a critical factor will ultimately lead to serious misinterpretations of the results and outcomes.…”