Mode of action of silver-based perovskite against Gram-negative bacteria

ABSTRACT Although silver is known for its antibacterial activity, its exact mode of action remains unclear. In our previous work, we described AgNbO 3 nanoparticles (AgNbO 3 NPs) prepared using a ceramic method, followed by high-energy and low-energy ball-milling processes, which exhibited antimicrobial activity with negligible release of Ag + in deionized water. Here, we investigated thoroughly the mode of action of these AgNbO 3 NPs against Escherichia coli . Drastic morphological changes in E. coli were observed after their exposure to AgNbO 3 NPs. In addition to cellular damage, AgNbO 3 NPs induced the production of reactive oxygen species and lipid peroxidation, likely following the release of small amounts of Ag + . This was concluded from the characterization of mutants resistant to AgNbO 3 NPs that showed cross-resistance to AgNO 3 , impaired reactive oxygen species production and lipid peroxidation, and harbored a key mutation in a two-component regulatory system regulating an Ag + efflux pump. We calculated, however, that the quantity of Ag + released from AgNbO 3 NPs is not sufficient by itself to lead to bacterial death. We propose that bacterial contact with the AgNbO 3 NPs in combination with Ag + release is necessary for the mode of action of AgNbO 3 NPs. IMPORTANCE Silver is known for its antibacterial activity, but its exact mode of action remains unclear. Here, we investigated thoroughly the mode of action of AgNbO 3 nanoparticles against Escherichia coli . Our data suggest that AgNbO 3 nanoparticles have dual effects on the cell and that both are required for its lethal action.