Functional characterization of extracellular vesicles produced by Bacteroides gingivalis.

Extracellular vesicles of Bacteroides gingivalis (type strain 33277) were isolated, and some of their biological activities were characterized. The vesicles were obtained from a 2-day culture after ammonium sulfate precipitation, differential centrifugation, and dialysis. When viewed by electron microscopy, vesicles of approximately 50 nm predominated. The results indicated that the enriched vesicle fraction had a high proteolytic activity against collagen, Azocoll, and N-alpha-benzoyl-DL-arginine p-nitroanilide. The polypeptide pattern of the vesicles was similar but not identical to that of the outer membrane. The membrane vesicles could also promote bacterial adherence between homologous cells as well as mediate attachment between two noncoaggregating bacterial species. These vesicles could thus play an important role in periodontal diseases by serving as a vehicle for toxins and various proteolytic enzymes, as well as being involved in adherence.