The application of zero-valent iron particles (ZVI) for the treatment of heavily polluted environment and its biological effects have been studied for at least two decades. Still, information on the impact on bacterial metabolic pathways is lacking. This study describes the effect of microscale and nanoscale ZVI (mZVI and nZVI) on the abundance of different metabolic pathways in freshwater bacterial communities. The metabolic pathways were inferred from metabolism modelling based on 16S rRNA gene sequence data using paprica pipeline. The nZVI changed the abundance of numerous metabolic pathways compared to a less influencing mZVI. We identified the 50 most affected pathways, where 31 were related to degradation, 17 to biosynthesis, and 2 to detoxification. The linkage between pathways was two times higher in nZVI samples compared to mZVI, and was specifically higher considering the arsenate detoxification II pathway. Limnohabitans and Roseiflexus were linked to the same pathways in both nZVI and mZVI. The prediction of metabolic pathways increases our knowledge of the impacts of nZVI and mZVI on freshwater bacterioplankton.

• MeSH
• Water Pollutants, Chemical * MeSH
• Chloroflexi * MeSH
• Genes, rRNA MeSH
• RNA, Ribosomal, 16S genetics   MeSH
• Fresh Water MeSH
• Iron MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Water Pollutants, Chemical * MeSH
• RNA, Ribosomal, 16S MeSH
• Iron MeSH

Due to their enhanced reactivity, metal and metal-oxide nanoscale zero-valent iron (nZVI) nanomaterials have been introduced into remediation practice. To ensure that environmental applications of nanomaterials are safe, their possible toxic effects should be described. However, there is still a lack of suitable toxicity tests that address the specific mode of action of nanoparticles, especially for nZVI. This contribution presents a novel approach for monitoring one of the most discussed adverse effects of nanoparticles, i.e., oxidative stress (OS). We optimized and developed an assay based on headspace-SPME-GC-MS analysis that enables the direct determination of volatile oxidative damage products (aldehydes) of lipids and proteins in microbial cultures after exposure to commercial types of nZVI. The method employs PDMS/DVB SPME fibers and pentafluorobenzyl derivatization, and the protocol was successfully tested using representatives of bacteria, fungi, and algae. Six aldehydes, namely, formaldehyde, acrolein, methional, benzaldehyde, glyoxal, and methylglyoxal, were detected in the cultures, and all of them exhibited dose-dependent sigmoidal responses. The presence of methional, which was detected in all cultures except those including an algal strain, documents that nZVI also caused oxidative damage to proteins in addition to lipids. The most sensitive toward nZVI exposure in terms of aldehyde production was the yeast strain Saccharomyces cerevisiae, which had an EC50 value of 0.08 g/L nZVI. To the best of our knowledge, this paper is the first to document the production of aldehydes resulting from lipids and proteins as a result of OS in microorganisms from different kingdoms after exposure to iron nanoparticles.

• Keywords
• Nanomaterial, Oxidative stress, Remediation, SPME, Toxicity assay, Yeast,
• MeSH
• Aldehydes pharmacology   MeSH
• Bacteria drug effects   MeSH
• Metal Nanoparticles toxicity   MeSH
• Lipids MeSH
• Nanostructures MeSH
• Oxidation-Reduction MeSH
• Oxidative Stress physiology   MeSH
• Toxicity Tests MeSH
• Ferric Compounds MeSH
• Iron metabolism   toxicity   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Aldehydes MeSH
• ferric oxide MeSH Browser
• Lipids MeSH
• methional MeSH Browser
• Ferric Compounds MeSH
• Iron MeSH

Two types of nano-scale zero-valent iron (nZVI-B prepared by borohydride reduction and nZVI-T produced by thermal reduction of iron oxide nanoparticles in H2) and a micro-scale ZVI (mZVI) were compared for PCB degradation efficiency in water and soil. In addition, the ecotoxicity of nZVI-B and nZVI-T particles in treated water and soil was evaluated on bacteria, plants, earthworms, and ostracods. All types of nZVI and mZVI were highly efficient in degradation of PCBs in water, but had little degradation effect on PCBs in soil. Although nZVI-B had a significant negative impact on the organisms tested, treatment with nZVI-T showed no negative effect, probably due to surface passivation through controlled oxidation of the nanoparticles.

• Keywords
• Bacteria, Earthworms, Ecotoxicity, Ostracods, Plants, Polychlorinated biphenyls, Remediation, Zero-valent iron nanoparticles and microparticles,
• MeSH
• Bacteria drug effects   MeSH
• Crustacea drug effects   MeSH
• Soil Pollutants toxicity   MeSH
• Nanoparticles MeSH
• Oligochaeta drug effects   MeSH
• Oxidation-Reduction MeSH
• Polychlorinated Biphenyls chemistry   MeSH
• Soil chemistry   MeSH
• Environmental Restoration and Remediation * MeSH
• Iron chemistry   pharmacology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Soil Pollutants MeSH
• Polychlorinated Biphenyls MeSH
• Soil MeSH
• Iron MeSH