Bacterial Extracellular Vesicles in the Strategic Interplay Between Pathogens and Hosts.

Bacterial extracellular vesicles (BEVs) are nanoscale spherical lipid bilayer structures secreted by bacteria, including outer membrane vesicles (OMVs) released by Gram-negative bacteria and membrane vesicles (MVs) produced by Gram-positive bacteria. Although the biogenesis of BEVs requires substantial energy expenditure, these vesicles provide bacteria with strategic advantages in the evolutionary interplay between pathogens and hosts. BEVs contribute to bacterial adaptation to environmental stress by remodeling membrane components, eliminating toxic substances, promoting biofilm formation, and mediating the interbacterial transfer of antibiotic resistance determinants. They can also function as decoys to protect bacteria from bacteriophage or antibiotic attack, deliver virulence factors, modulate host immune responses to facilitate bacterial colonization, and mediate interspecies competition. This review summarizes the central roles of BEVs as bacterial mediators of environmental responses, with particular emphasis on their involvement in immune regulation, environmental adaptation, and interspecies competition, thereby providing new insights into pathogen evolutionary strategies.