Research into how microbial organisms are adapting to the ever increasing levels of nanoparticles is important in assessing the impact of nanomaterials on various environmental systems and processes. However, the surprising ability of microorganisms to turn metals in the environment into nanoparticles is often overlooked and could be making a significant contribution to this rise of nanoparticles in the environment.
In this HOT article, Monika Mortimer et al. study the ability of Tetrahymena thermophile, a fresh-water inhabiting protozoa, to reduce silver ions to silver nanoparticles. It is the soluble extracellular fraction (SEF) of the protozoa in which this occurs. The team demonstrate that the protein fraction of this SEF is associated with the formation of silver nanoparticles.
The ability of some microorganisms to carry out this conversion is surprising due to the toxicity of many silver compounds and the well-known antibacterial properties of silver nanoparticles.
In this study, the protozoa do show a negative response to the silver compound (AgNO3) within 2 hours of exposure, but then they convert AgNO3 to less toxic nanoparticles, resulting in a recovery period over 24 hours. This supports the theory that it is not silver nanoparticles themselves that cause the toxicity but remaining dissolved silver ions.
This HOT article increases our knowledge of this surprising defence mechanism against toxic silver compounds and adds evidence to the ongoing debate surrounding the mechanism of toxicity of silver nanoparticles.
This article is free to access for 4 weeks*, read it by clicking the link below:
Extracellular conversion of silver ions into silver nanoparticles by protozoan Tetrahymena thermophila
Katre Juganson, Monika Mortimer, Angela Ivask, Kaja Kasemets and Anne Kahru
DOI: 10.1039/C2EM30731F
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