Impact of Ag and Al2O3 nanoparticles on soil organisms: In vitro and soil experiments

• Published in: The Science of the total environment 2014-03, Vol.473-474, p.254-261
• Main Authors: Fajardo, C., Saccà, M.L., Costa, G., Nande, M., Martin, M.
• Format: Article
• Language: English
• Subjects: Aluminum - toxicity; Aluminum oxide; Animals; Bacillus cereus; Bacteria; C. elegans; Caenorhabditis elegans; Caenorhabditis elegans - drug effects; Cytotoxicity; Exposure; Gene Expression - drug effects; In vitro testing; Metal Nanoparticles - toxicity; Microorganisms; Nanoparticles; Oxidative Stress; Pseudomonas stutzeri; Silver; Silver - toxicity; Soil; Soil (material); Soil Pollutants - toxicity; Toxicity
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2013.12.043

In vitro analyses were conducted to assess the impact of Al2O3 and Ag nanoparticles on two common soil bacteria, Bacillus cereus and Pseudomonas stutzeri. Al2O3 nanoparticles did not show significant toxicity at any dose or time assayed, whereas exposure to 5mgL−1 Ag nanoparticles for 48h caused bactericidal effects. Moreover, alterations at the morphological level were observed by transmission electron microscopy (TEM); Ag but not Al2O3 nanoparticles evoked the entrance of B. cereus cells in an early sporulation stage and both nanoparticles penetrated P. stutzeri cells. At the molecular level, a dramatic increase (8.2-fold) in katB gene expression was found in P. stutzeri following Al2O3 nanoparticles exposure, indicative of an oxidative stress-defence system enhancement in this bacterium. In the microcosm experiment, using two different natural soils, Al2O3 or Ag nanoparticles did not affect the Caenorhabditis elegans toxicity endpoints growth, survival, or reproduction. However, differences in microbial phylogenetic compositions were detected by fluorescence in situ hybridization (FISH). The use of katB- and pykA-based sequences showed that the microbial transcriptional response to nanoparticle exposure decreased, suggesting a decrease in cellular activity. These changes were attributable to both the nanoparticles treatment and soil characteristics, highlighting the importance of considering the soil matrix on a case by case basis. •Al2O3 or Ag NPs impact on bacteria was assessed at phenotypic and molecular level.•katB gene involved in oxidative-stress response was overexpressed in P. stutzeri following Al2O3 NPs exposure.•A decrease in bacterial transcriptional response was detected in NPs-treated soils.•A soil-dependent response to specific NP treatment was observed.•In NPs-treated soils no acute toxic effects on C. elegans were found.