Related Experiment Video
Updated: Jan 31, 2026
Improved Enzyme Protection Assay to Study Staphylococcus aureus Internalization and Intracellular Efficacy of Antimicrobial Compounds
Published on: September 8, 2021
The AGXX® Antimicrobial Coating Causes a Thiol-Specific Oxidative Stress Response and Protein S-bacillithiolation in
Vu Van Loi1, Tobias Busche1,2, Thalia Preuß1
1Institute for Biology-Microbiology, Freie Universität Berlin, Berlin, Germany.
Abstract:
Multidrug-resistant pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA) pose an increasing health burden and demand alternative antimicrobials to treat bacterial infections. The surface coating AGXX® is a novel broad-spectrum antimicrobial composed of two transition metals, silver and ruthenium that can be electroplated on various surfaces, such as medical devices and implants. AGXX® has been shown to kill nosocomial and waterborne pathogens by production of reactive oxygen species (ROS), but the effect of AGXX® on the bacterial redox balance has not been demonstrated. Since treatment options for MRSA infections are limited, ROS-producing agents are attractive alternatives to combat multi-resistant strains. In this work, we used RNA-seq transcriptomics, redox biosensor measurements and phenotype analyses to study the mode of action of AGXX® microparticles in S. aureus USA300. Using growth and survival assays, the growth-inhibitory amount of AGXX® microparticles was determined as 5 microg/ml. In the RNA-seq transcriptome, AGXX® caused a strong thiol-specific oxidative stress response and protein damage as revealed by the induction of the PerR, HypR, QsrR, MhqR, CstR, CtsR, and HrcA regulons. The derepression of the Fur, Zur, and CsoR regulons indicates that AGXX® also interferes with the metal ion homeostasis inducing Fe2+- and Zn2+-starvation responses as well as export systems for toxic Ag+ ions. The induction of the SigB and GraRS regulons reveals also cell wall and general stress responses. AGXX® stress was further shown to cause protein S-bacillithiolation, protein aggregation and an oxidative shift in the bacillithiol (BSH) redox potential. In phenotype assays, BSH and the HypR-controlled disulfide reductase MerA were required for protection against ROS produced under AGXX® stress in S. aureus. Altogether, our study revealed a strong thiol-reactive mode of action of AGXX® in S. aureus USA300 resulting in an increased BSH redox potential and protein S-bacillithiolation.
Insights
The novel antimicrobial coating AGXX® combats methicillin-resistant Staphylococcus aureus (MRSA) by inducing thiol-specific oxidative stress and disrupting metal ion homeostasis. This broad-spectrum agent offers a promising alternative for treating resistant bacterial infections.
Area of Science:
- Microbiology and Antimicrobial Research
- Materials Science and Surface Coatings
- Biochemistry and Redox Biology
Background:
- Multidrug-resistant pathogens, including MRSA, present a significant global health challenge, necessitating novel antimicrobial strategies.
- The AGXX® surface coating, a composite of silver and ruthenium, demonstrates broad-spectrum antimicrobial activity via reactive oxygen species (ROS) production.
- The precise mechanism by which AGXX® impacts bacterial redox balance, particularly in MRSA, remains underexplored.
Purpose of the Study:
- To elucidate the mode of action of AGXX® microparticles against Staphylococcus aureus USA300.
- To investigate the effects of AGXX® on bacterial redox balance, thiol reactivity, and metal ion homeostasis.
- To identify key bacterial responses and protective mechanisms against AGXX®-induced stress.
Main Methods:
- RNA-sequencing (RNA-seq) transcriptomics to analyze gene expression changes.
- Redox biosensor measurements to assess the bacillithiol (BSH) redox potential.
- Phenotype analyses, including growth and survival assays, to evaluate AGXX®'s antimicrobial efficacy and identify essential protective genes.
Main Results:
- AGXX® at 5 µg/ml induced significant thiol-specific oxidative stress, evidenced by the upregulation of multiple regulons (PerR, HypR, QsrR, MhqR, CstR, CtsR, HrcA).
- AGXX® disrupted metal ion homeostasis, leading to Fe2+ and Zn2+ starvation responses and increased export of Ag+ ions, indicated by derepression of Fur, Zur, and CsoR regulons.
- AGXX® exposure resulted in protein S-bacillithiolation, protein aggregation, an oxidative shift in BSH redox potential, and required BSH and MerA for protection against ROS.
Conclusions:
- AGXX® exerts its antimicrobial effect through potent thiol reactivity, leading to widespread protein damage and oxidative stress in Staphylococcus aureus.
- The disruption of metal ion homeostasis and induction of general stress responses further contribute to AGXX®'s efficacy against MRSA.
- Understanding AGXX®'s thiol-reactive mechanism provides a basis for developing new antimicrobial strategies targeting resistant bacterial strains.
Related Concept Videos
02:45Responses to Heat and Cold Stress
02:02Responses to Salt Stress
01:23Antimicrobial Proteins
Interferons
Interferons (IFNs) are proteins produced by lymphocytes, macrophages, and fibroblasts infected with viruses. While IFNs cannot prevent viruses from entering and...
01:21Stress Response System
Alarm stage
In the alarm stage, the body's...
01:20Psychological Responses to Stress
01:30Other Stress Responses in Bacteria