Bacterial Extracellular Vesicles at the Crossroads of Immune Regulation and Biofilm Dynamics: Biogenesis, Comparative Analysis, and Translational Challenges

Bacterial extracellular vesicles (BEVs) are nano-sized lipid bilayer particles secreted by bacteria, capable of carrying various proteins, lipids, nucleic acids, and pathogen-associated molecular patterns (PAMPs). The biosynthetic pathway of BEVs determines their load components, physicochemical properties, and different biological activities. Increasing evidence indicates that BEVs play an important role in mediating host immune responses and the dynamic regulation of bacterial biofilms. Additionally, BEVs may serve as a molecular bridge between the two. BEVs derived from pathogens can trigger pro-inflammatory cascades, assist bacteria in immune evasion, and further accelerate the maturation of biofilms, forming a vicious cycle of persistent infection and inflammatory damage. In contrast, BEVs derived from probiotics can maintain host immune homeostasis and exert direct anti-biofilm and synergistic antibacterial effects, thereby breaking the pathological cycle. However, significant methodological research bottlenecks have greatly hindered the comparability and clinical translation of BEVs research. This article systematically summarizes the classification of BEVs and their biosynthetic mechanisms, compares the differential effects of BEVs from pathogenic bacteria and probiotic bacteria on immunity, clarifies the dual regulatory role of BEVs throughout the life cycle of biofilms, and highlights the bridging function of BEVs in the immune–biofilm interaction. Additionally, this article also discusses the current development of BEVs in clinical translation applications, such as vaccine development, antibiotic delivery, and mucosal inflammation intervention, and outlines the key industrial and clinical challenges faced in the future development of BEVs-based therapeutic approaches.