Bacterial Extracellular Vesicles: An Emerging Concern in the Field of Environmental Contamination—Characterization, Impacts, and Response Strategies

Bacterial extracellular vesicles (BEVs) are nanoscale membrane-bound structures secreted by prokaryotic cells and have recently gained considerable attention in environmental pollution research. By encapsulating virulence factors and antibiotic resistance genes (ARGs), BEVs can persist in aquatic, soil, and sedimentary environments, facilitating interspecies gene transfer, aggravating microbial contamination, and ultimately posing risks to ecosystem stability and human health. This review provides a comprehensive overview of BEVs' formation mechanisms, structural composition, and spatial distribution. Particular attention is given to the environmental implications of BEVs, including their roles in mediating horizontal ARG transfer, delivering virulence genes and amplifying pathogenicity, and their emerging potential as environmental bioindicators, despite current analytical limitations in complex matrices. Nevertheless, three major research gaps remain: (i) the molecular mechanisms underlying BEV interactions with heavy metals and microplastics are poorly understood; (ii) field-based quantification and distribution data are still limited; and (iii) effective, targeted strategies for BEV removal or inactivation are lacking. Addressing these challenges will not only enhance our understanding of BEV-mediated environmental risks but also inform the development of advanced detection methods and remediation approaches for BEV-associated pollution.