Silver-coated carbon nanotubes downregulate the expression of Pseudomonas aeruginosa virulence genes: a potential mechanism for their antimicrobial effect.
The antimicrobial activity of silver-coated carbon nanotubes (AgCNTs) and their potential mode of action against mucoid and nonmucoid strains of Pseudomonas aeruginosa was investigated in vitro. The results showed that AgCNTs exhibited antimicrobial activity against both strains with minimum inhibitory concentrations of approximately 8 µg/mL, indicating a high sensitivity of P. aeruginosa to AgCNTs. AgCNTs were also bactericidal against both strains at the same minimum inhibitory concentration. Scanning and transmission electron-microscopy studies further revealed that a majority of the cells treated with AgCNTs transformed from smooth rod-shape morphology to disintegrated cells with broken/damaged membranes, resulting in leakage of cytoplasmic contents to produce ghost cells. The molecular effects of AgCNTs on P. aeruginosa genes involved in virulence and pathogenicity, stress response, and efflux pumps were evaluated for changes in their expression. Quantitative real-time PCR (qRT-PCR) showed that after exposure to AgCNTs, the expression levels of the rpoS, rsmZ, and oprD genes were significantly downregulated in both strains of P. aeruginosa compared to the untreated samples. These results suggest that the mechanism of action of AgCNTs may be attributed to their effect on cell-membrane integrity, downregulation of virulence-gene expression, and induction of general and oxidative stress in P. aeruginosa.
Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, USA.
Ejovwoke
E
Dosunmu
Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, USA.
Atul A
AA
Chaudhari
Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, USA.
Shree R
SR
Singh
Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, USA.
Vida A
VA
Dennis
Center for NanoBiotechnology Research, Alabama State University, Montgomery, AL, USA.
Shreekumar R
SR
Pillai
D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D020099:Coated Materials, Biocompatible / Q000737:chemistry / Q000494:pharmacology; D015536:Down-Regulation; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D005798:Genes, Bacterial; D008826:Microbial Sensitivity Tests; D046529:Microscopy, Electron, Transmission; D037742:Nanotubes, Carbon / Q000737:chemistry*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics*; D012329:RNA, Bacterial / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012834:Silver / Q000737:chemistry / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D020099:Coated Materials, Biocompatible; D037742:Nanotubes, Carbon; D012329:RNA, Bacterial; D012834:Silver
AgCNT; Pseudomonas aeruginosa; antimicrobial activity; qRT-PCR