The mechanisms of toxicity of silver nanoparticles (AgNPs) are not clear and the role of Ag+ released
from the nanoparticulated form in the overall toxicity requires further attention, especially in aquatic
ecosystems where NPs will most likely end up. The impacts of AgNPs and Ag+ were assessed based
on the variations in the overall proteome in i) two aquatic fungal ecotypes of Articulospora tetracladia, one isolated from a non-polluted stream (At72) and the other from a metal-polluted stream
(At61), and ii) the bacterial strain Pseudomonas sp. M1 (PsM1) isolated from a metal-polluted
stream. Transcriptomic responses of At72 in the same exposure conditions were also assessed to
complement knowledge from proteomic responses. At72 was the most sensitive to AgNPs, whereas
PsM1 was the most tolerant one. The toxicity of AgNPs was supported by data from NP characterization, which showed increased particle stability and lesser agglomeration in presence of At72
that the other microbes. Omic responses to equitoxic levels of AgNPs and Ag+ suggested different
mechanisms of toxicity since distinct profiles of protein and gene expression were unveiled. Gene
Ontology (GO) enrichment analysis further unravelled several biological processes and allowed to
differentiate the effects of AgNPs from those of Ag+. Overall, omic approaches revealed different
adaptive responses to Ag+ or AgNPs in the metabolic, energetic and stress pathways. Furthermore,
the negligible amount of Ag+ released from AgNPs suggested that toxicity of AgNPs was mainly
associated with the particle for