title: Differential gene regulation in the Ag nanoparticle and Ag(+)-induced silver stress response in Escherichia coli: a full transcriptomic profile.
abstract: We report the whole-transcriptome response of Escherichia coli bacteria to acute treatment with silver nanoparticles (AgNPs) or silver ions [Ag(I)] as silver nitrate using gene expression microarrays. In total, 188 genes were regulated by both silver treatments, 161 were up-regulated and 27 were down-regulated. Significant regulation was observed for heat shock response genes in line with protein denaturation associated with protein structure vulnerability indicating Ag(I)-labile -SH bonds. Disruption to iron-sulphur clusters led to the positive regulation of iron-sulphur assembly systems and the expression of genes for iron and sulphate homeostasis. Further, Ag ions induced a redox stress response associated with large (>600-fold) up-regulation of the E. coli soxS transcriptional regulator gene. Ag(I) is isoelectronic with Cu(I), and genes associated with copper homeostasis were positively regulated indicating Ag(I)-activation of copper signalling. Differential gene expression was observed for the silver nitrate and AgNP silver delivery. Nanoparticle delivery of Ag(I) induced the differential regulation of 379 genes; 309 genes were uniquely regulated by silver nanoparticles and 70 genes were uniquely regulated by silver nitrate. The differential silver nanoparticle-silver nitrate response indicates that the toxic effect of labile Ag(I) in the system depends upon the mechanism of delivery to the target cell.
authors.affiliation: Department of Biosciences, College of Life and Environmental Sciences, University of Exeter , Exeter , UK.
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: McQuillan
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Shaw
mesh_terms: D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics; D005786:Gene Expression Regulation; D053768:Metal Nanoparticles; D012834:Silver / Q000737:chemistry / Q000494:pharmacology*; D059467:Transcriptome
chemical_list: D012834:Silver
keywords: Mechanism; microarray; nanoparticle; silver; toxicity