Fig. 1: Toxicity of AgNPs to Caenorhabditis elegans colonized by different bacteria.

a Transmission electron microscopy and (b) dynamic light scattering results demonstrate the high dispersibility of AgNPs in deionized water. c Survival rate, head thrash, body length, and reproduction of germ-free (GF) C. elegans exposed to different concentrations (1.76, 5.3, 17.6, 53, 176, or 1144 μg/m²) of AgNPs versus the unexposed control treatment. d Reproduction in GF C. elegans and C. elegans colonized by active bacteria (P.m.—P. mendocina, E.c.—E. coli, Cmm.—Comamonas sp., C.p.—C. piscis) when exposed to different concentrations (1.76, 5.3, 17.6, 53, 176, or 1144 μg/m²) of AgNPs versus that in the respective unexposed control. e Top 20 Gene Ontology (GO) pathways enriched in differentially expressed genes of GF C. elegans exposed for 55 h to 17.6 μg/m² of AgNPs as compared to the control treatment without any exposure of AgNPs. P values were corrected using the Bonferroni method for multiple testing following Fisher’s exact test. f Heat map of the expression of genes related to the MAPK and oocyte maturation pathways in GF nematodes exposed or not (Ctrl) to 17.6 μg/m² of AgNPs and in those colonized by the four bacterial species and exposed to the same concentration of AgNPs. Lines in (c, d) are dose-response curves simulated by a four-parameter logistic model. To enable the logarithmic scale depiction of the data in the unexposed control treatment (c, d), a nominal AgNP concentration of 0.01 μg/m² was applied to this treatment, despite the absence of actual exposure. Data in (b–d) are the mean ± standard deviation (n = 3 independent experiments).