Fig 1.
Size characterization of nanoparticles.
(A) Dynamic light scattering (DLS) was used to assess the size of ZnONPs and AgNPs. Mean ± SEM are presented (n ≥ 3). (B) Transmission electron microscopy images of ZnONPs and AgNPs (Note: the scale bars are 200 and 20 nm for ZnONPs and AgNPs, respectively).
Fig 2.
Functional distribution of deletion mutants that are highly sensitive to ZnONPs and AgNPs.
(A) Clustering of the 59 most sensitive deletion mutant strains to 1 mg/mL ZnONPs reveal that mutants lacking genes involved in membrane and transmembrane transport, ion homeostasis and transport, and cell organization of biogenesis encompass the significantly enriched groups. (B) Clustering of the 96 most sensitive deletion mutant strains to 0.095 mg/mL AgNPs indicate that mutants lacking genes involved in transcription, cellular respiration, and endocytosis and vesicular transport represent the significantly enriched groups.
Fig 3.
Cell membrane disruption by ZnONPs.
(A) Carboxyfluorescein leakage from liposomes that were exposed to various concentrations of ZnONPs for 30 min. (B) Trypan blue exclusion assay in yeast cells following a 2 h exposure to various concentrations of ZnONPs. Mean ± SEM are presented (n ≥ 3). Significant differences are indicated with letters. (C) Membrane depolarization analysis in yeast cells that were subjected to: 0.01 mM citric acid (negative control), 20 μM CCCP (carbonyl cyanide 3-chlorophenylhydrazone; positive control), and 1 mg/mL ZnONPs. The histograms show the number (Count, Y-axis) of yeast cells in a sample with depolarized membranes (FL2-H interval = 104–105) and cells at resting potential (FL2-H = 102–104).
Fig 4.
ZnONPs compromise cell wall integrity.
(A) Cells were exposed to various concentrations of ZnONPs, subjected to mild sonication, diluted and then spotted onto YPD and compared to non-sonicated counterparts. (B) Cell survival rate (% survival sonicated/non-sonicated cells) was then quantified. Mean ± SEM are presented (n ≥ 3). Significant differences are indicated with letters.
Fig 5.
Transcription rate, cellular respiration, and endocytosis in yeast cells exposed to AgNPs.
(A) β-galactosidase reporter gene expression assay was used to estimate transcription rate in response to AgNPs or 6-azauracil (positive control). β-galactosidase activity in treatments is expressed relative to no-AgNPs control (negative control). (B) MTT reduction assay was used to estimate cellular respiration in response to AgNPs or sodium azide (positive control). (C) Brightfield, fluorescence, and merged images of negative control, AgNPs (80 μg/mL), and positive control (NaN3) groups. The cells that internalized Lucifer Yellow (LY) are fluorescent. (D) The uptake of LY was used to estimate endocytosis in response to AgNPs. Percentage of fluorescent cells relative to control was determined by examining at least 6 different fields, each with >20 cells. Mean ± SEM are presented (n ≥ 3). Significant differences are indicated with letters.