The effects of nanomaterials have been primarily assessed based on standard ecotoxicity guidelines. However, by adapting alternative measures the information gained could be enhanced considerably, e.g., studies should focus on more mechanistic approaches. Here, the environmental risk posed by the presence of silver nanoparticles (Ag NM300K) in soil was investigated, anchoring population and cellular level effects, i.e., survival, reproduction (28 days) and oxidative stress markers (0, 2, 4, 6, 10 days). The standard species Folsomia candida was used. Measured markers included catalase (CAT), glutathione reductase (GR), glutathione S-transferase (GST), total glutathione (TG), metallothionein (MT) and lipid peroxidation (LPO). Results showed that AgNO3 was more toxic than AgNPs at the population level: reproduction EC20 and EC50 was ca. 2 and 4 times lower, respectively. At the cellular level Correspondence Analysis showed a clear separation between AgNO3 and AgNP throughout time. Results showed differences in the mechanisms, indicating a combined effect of released Ag+ (MT and GST) and of AgNPs (CAT, GR, TG, LPO). Hence, clear advantages from mechanistic approaches are shown, but also that time is of importance when measuring such responses.

Although environmental effects are mostly assessed via standard individual species the ecological relevance of multispecies testing is well-recognized and highly recommended. Hence, the effect of copper oxide nanomaterials (CuONM) and CuCl were assessed using the validated soil multispecies system (SMS). Besides the individual species (IS) "standard" tests for all, a predation study was done. Toxicity was higher in the SMS than in the IS, and longer exposure showed increased toxicity. The predator ( Hypoaspis aculeifer) preyed most on smaller species, but the net biomass consumed was similar across species. Internal Cu in Folsomia candida reached ca. 140 μg Cu/g dry weight, fluctuating over time, especialy for CuCl. Copper was mostly bound to soil components for both Cu forms (<0.2% of the total Cu in soil solution, < 0.007% on the ionic form, but the soil solution content increased with the total added concentration). Hazard Concentrations (HC5) showed higher toxicity and more similarity between Cu forms at longer-term exposure. Risk of NMs is relatively limited at present (IS based instead of SMS) with short exposure times (i.e., longer is required) and too few IS tested. The impact of species interactions is highlighted and is of key importance to include in ecosystem hazard prediction.

Nasopharyngeal colonization is important for Streptococcus pneumoniae evolution, providing the opportunity for horizontal gene transfer when multiple strains co-occur. Although colonization with more than one strain of pneumococcus is common, the factors that influence the ability of strains to coexist are not known. A highly variable blp (bacteriocin-like peptide) locus has been identified in all sequenced strains of S. pneumoniae. This locus controls the regulation and secretion of bacteriocins, small peptides that target other bacteria. In this study, we analyzed a series of cocolonizing isolates to evaluate the impact of the blp locus on human colonization to determine whether competitive phenotypes of bacteriocin secretion restrict cocolonization. We identified a collection of 135 nasopharyngeal samples cocolonized with two or more strains, totaling 285 isolates. The blp locus of all strains was characterized genetically with regard to pheromone type, bacteriocin/immunity content, and potential for locus functionality. Inhibitory phenotypes of bacteriocin secretion and locus activity were assessed through overlay assays. Isolates from single colonizations (n ‫؍‬ 298) were characterized for comparison. Cocolonizing strains had a high diversity of blp cassettes; approximately one-third displayed an inhibitory phenotype in vitro. Despite in vitro evidence of competition, pneumococci cocolonized the subjects independently of blp pheromone type (P ‫؍‬ 0.577), bacteriocin/immunity content, blp locus activity (P ‫؍‬ 0.798), and inhibitory phenotype (P ‫؍‬ 0.716). In addition, no significant differences were observed when single and cocolonizing strains were compared. Despite clear evidence of blp-mediated competition in experimental models, the results of our study suggest that the blp locus plays a limited role in restricting pneumococcal cocolonization in humans. IMPORTANCENasopharyngeal colonization with Streptococcus pneumoniae (pneumococcus) is important for pneumococcal evolution, as the nasopharynx represents the major site for horizontal gene transfer when multiple strains co-occur, a phenomenon known as cocolonization. Understanding how pneumococcal strains interact within the competitive environment of the nasopharynx is of chief importance in the context of pneumococcal ecology. In this study, we used an unbiased collection of naturally co-occurring pneumococcal strains and showed that a biological process frequently used by bacteria for competition-bacteriocin production-is not decisive in the coexistence of pneumococci in the host, in contrast to what has been shown in experimental models. Streptococcus pneumoniae is an important bacterial pathogen associated with high morbidity and mortality worldwide (1-3). Notwithstanding, disease is a rare event compared with the frequency of asymptomatic nasopharyngeal colonization (4).Nasopharyngeal colonization is particularly frequent among young children (5), and multiple strains can be simultaneously detected in the same sample (6-8). As the pneumoco...