Fig. 2: BEV practices: source, preparation, and characterization.

a Source: BEVs are prepared from bacterial cell culture (93.6%; colors correspond to phyla in cladogram) or other sources (6.4%; gray/white; blood, feces, intestinal tissue, milk, saliva, urine and other) (right). Circular cladogram indicating the taxonomy of studied bacterial species. The outer circle shows studied phyla, with each color representing one phylum. Number of experiments per phylum is represented by the color of the cladogram species level (gray vs. blue for most abundant phylum Pseudomonadota). Number of experiments per species is indicated by the size of the circles on the outer layer of the species level. The three most abundant species are indicated in purple (and with arrow): E. coli, S. aureus, and P. aeruginosa (left). b Preparation: Bar plot indicating number of implemented methods: one (6%), two (48%), or more than two (46%). Chord diagram shows combination of reported preparation methods, with DUC (green) and filtration (blue) as most implemented methods. Other method includes commercial method, tangential flow filtration (TFF), density cushion and precipitation. c Characterization: Bar plot indicating number of implemented methods combined: zero (28.6%), one (38.4%) two (20%), or three or more (13%). Chord diagram shows combination of reported characterization methods, with most studies performing no biochemical (orange) or biophysical characterization (pink). Other method includes PAMP reporter assays, multi-angle light scattering (MALS), confocal microscopy, spectrophotometry. BEV bacterial extracellular vesicle, DLS dynamic light scattering, DUC differential (ultra-)filtration, E. coli Escherichia coli, ELISA enzyme linked immune sorbent assay, NTA nanoparticle tracking analysis, P. aeruginosa Pseudomonas aeruginosa, S. aureus Staphylococcus aureus, SDS-PAGE sodium dodecyl-sulfate polyacrylamide gel electrophoresis, SEC size exclusion chromatography, TRPS tunable resistive pulse sensing.