Bacterial extracellular membrane vesicles as multifunctional defense systems: Roles in immune evasion, phage interactions, and antimicrobial resistance.

Bacterial extracellular membrane vesicles (EMVs) are multifunctional nanoparticles released by Gram-negative and Gram-positive bacteria, which are involved in microbial ecology and pathogenesis. Their functions include facilitating intercellular communication, biofilm development, and nutrient acquisition within microbial communities, host-microbe interactions, and modulating host immune responses. EMVs help bacteria adapt and survive in different environments by serving as detergents, mediators in biochemical cycles, and defense systems. EMVs contain immunomodulatory components that interfere with host immune signaling pathways, allowing bacteria to evade the immune system. EMVs sequester antimicrobial peptides, thereby attenuating their antimicrobial efficacy. Additionally, EMVs are responsible for the transmission of antibiotic resistance, storage of resistance determinants and efflux pumps, and regulation of the action of antimicrobial drugs. The interactions between EMVs and bacteriophages add a degree of complexity, as EMVs can serve as protective barriers against viral entities and influence phage-bacteria interactions by binding and encapsulating bacteriophages. EMVs in biofilms may facilitate communication and cooperation among bacterial cells, which increases their survival capabilities against antimicrobials. This review comprehensively discusses EMVs' defenses against host immune responses, bacteriophage, and antimicrobials, which is vital for developing potential treatment techniques and combating antibiotic resistance.