Emerging strategies of bacterial adaptation mechanisms to silver and metal oxide nanomaterials

This review addresses the crucial and emerging field of bacterial adaptation to antimicrobial nanomaterials, challenging prior assumptions that their multi-level action prevents the development of reduced bacterial sensitivity. It provides a comprehensive overview of experimentally induced adaptation mechanisms across various nanomaterials (e.g. AgNPs, ZnO) and bacterial species. Bacterial adaptations encompass genetic adaptations (e.g. efflux systems, mutagenesis), biomolecule production (e.g. flagellin, exopolysaccharides forming biofilms, protein coronas), and structural changes (e.g. altered shape, cell wall thickening, enhanced motility, membrane permeability changes). The described adaptation mechanisms to nanomaterials are compared with antibiotic resistance mechanisms, emphasizing common strategies such as efflux and envelope changes, but also unique adaptations specific to nanoparticles, such as aggregation and different roles of biomolecules. The review offers insights and emerging strategies for designing safer, more effective nano-antimicrobials, including membrane potential disruption, biofilm inhibition, and size modulation. It emphasizes the need for standardized evaluation methods and future research on cross-resistance.