What can be inferred from bacterium–nanoparticle interactions about the potential consequences of environmental exposure to nanoparticles?

Abstract

This article collates published information regarding the in vitro antibacterial activity of both metal and carbon nanoparticles. The aims are to establish a consensus regarding modes of antibacterial activity, and to evaluate the applicability of current knowledge to prediction of likely effects of nanoparticles upon important microbial processes in environmental exposures. The majority of studies suggest that nanoparticles cause disruption to bacterial membranes, probably by production of reactive oxygen species. Contact between the nanoparticle and bacterial membrane appears necessary for this activity to be manifested. Interfacial forces such as electrostatic interactions are probably important in this respect. However, the toxicity of free metal ions originating from the nanoparticles cannot be discounted. Passage of nanoparticles across intact membranes appears to be unlikely, although accumulation within the cytoplasm, probably after membrane disruption, is often observed. To date, published studies have not been designed to mimic natural systems and therefore provide poor understanding of the likely consequences of intentional or unintentional environmental release. The limited studies currently available fail to identify any significant effects at the microbial level of nanoparticles in more complex systems.

Ecotoxicity test methods for engineered nanomaterials: Practical experiences and recommendations from the bench

“…The suggestion of including a benthic grazing test to the base set of ecotoxicity tests (discussed previously) could apply equally to microbes given their importance to biofilms at the base of food webs. Bacteria have been shown to be very sensitive to exposure to a variety of ENMs, including carbon nanotubes, ZnO, CdSe, and TiO 2 [107,108]. Silver nanoparticles have been studied extensively in the laboratory and have significant inhibitory effects on bacterial growth and activity [107,109,110], although Ag ions released by the NPs could have contributed to this toxicity [111,112].…”

“…Bacteria have been shown to be very sensitive to exposure to a variety of ENMs, including carbon nanotubes, ZnO, CdSe, and TiO 2 [107,108]. Silver nanoparticles have been studied extensively in the laboratory and have significant inhibitory effects on bacterial growth and activity [107,109,110], although Ag ions released by the NPs could have contributed to this toxicity [111,112]. Alterations to microbial communities could have significant effects on biogeochemical cycling and other critical ecosystem services [113].…”

The potential health risk of titania nanoparticles

“…Although TNPs showed only slight effects on D. magna mortality, its reproduction was severely affected by chronic exposure [78]. The ecotoxicity of TNP is ROS-mediated damage to organisms induced by TNP accumulation, disruption of membranes, and other oxidative stress responses [76,79]. TNP micelles or protein-coated TNPs were easily internalized by Salmonella typhimurium [80].…”

Morphology-dependent bactericidal activities of Ag/CeO2 catalysts against Escherichia coli

“…The antimicrobial properties of nanoscale metal and metal oxide particles such as Ag, TiO 2 , ZnO, and MgO have been the focus of research and application in antimicrobial coatings. Such metal nanoparticles interact with microbial cells through multiple biochemical pathways, for instance, via the production of reactive oxygen species (ROS) such as •OH, H 2 O 2 , and •O 2 − , which can damage cell structures and ultimately cause cell death [4][5][6][7][8]. Generally, photocatalysts such as TiO 2 can effectively produce ROS when applied in water [9,10].…”