title: Impact of Ag and Al₂O₃ nanoparticles on soil organisms: in vitro and soil experiments.
abstract: 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 5 mg L(-1) Ag nanoparticles for 48 h 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.
authors.affiliation: Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain. Electronic address: carmen.fajardo@vet.ucm.es.
authors.forename: C
authors.initials: C
authors.lastname: Fajardo
authors.affiliation: Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain; Campus de Excelencia Internacional de Moncloa, 28040 Madrid, Spain. Electronic address: marialudovicasacca@pdi.ucm.es.
authors.forename: M L
authors.initials: ML
authors.lastname: Saccà
authors.affiliation: Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain. Electronic address: costag@vet.ucm.es.
authors.forename: G
authors.initials: G
authors.lastname: Costa
authors.affiliation: Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain. Electronic address: mnande@vet.ucm.es.
authors.forename: M
authors.initials: M
authors.lastname: Nande
authors.affiliation: Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain. Electronic address: margamar@vet.ucm.es.
authors.forename: M
authors.initials: M
authors.lastname: Martin
mesh_terms: D000535:Aluminum / Q000633:toxicity*; D000818:Animals; D017173:Caenorhabditis elegans / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D053768:Metal Nanoparticles / Q000633:toxicity*; D018384:Oxidative Stress; D012834:Silver / Q000633:toxicity*; D012987:Soil; D012989:Soil Pollutants / Q000633:toxicity*
chemical_list: D012987:Soil; D012989:Soil Pollutants; D012834:Silver; D000535:Aluminum
keywords: Bacteria; C. elegans; Cytotoxicity; Nanoparticles; Soil