Isolation and characterization of Faecalibacterium prausnitzii extracellular vesicles

Introduction: Extracellular vesicles (EVs) contain active biological compounds which play important roles in biological processes. The secretion of EVs is a common phenomenon which occurs in archaea, bacteria and mammalian cells. The secretion of bacterial EVs has been discovered in various species of both Gram-negative and Gram-positive bacteria. Faecalibacterium prausnitzii is one of the commensal bacteria in human intestinal tract which has potentially therapeutic effects by secretion of bioactive compounds. Within the last few years, many investigations have been performed with respect to extracting and obtaining EVs and as a result, there are many methods to isolate and characterize EVs. The aim of this study was to isolate EVs from F. prausnitzii strain A2-165 and to characterize their physico-chemical properties. Methods: EVs were isolated from F. prausnitzii strain A2-165 using ultracentrifugation and filtration. The EVs of bacterium were then characterized by Scanning Electron Microscopy, SDS-PAGE, Bradford assay, NanoDrop and Limulus Amebocyte Lysate (LAL) test. Results: The extracted EVs were confirmed with the shape of vesicles and the sizes ranging from ~ 30 to 250 nm. Total protein concentration of EVs were ~ 3 mg/ml from two methods; Bradford and NanoDrop, respectively. Protein profile pattern of F. prausnitzii-derived EVs ranged from 11 up to 245 kDa. Endotoxin measurement was 2.04 EU/ml. Conclusion: The results of the current study demonstrated that EVs purity and conformation were acceptable. However, further investigations are necessary to elucidate the safety, efficacy, practicality and mechanism of action of this bacterium EVs in clinical practices, especially as vaccine delivery vehicles in the field of vaccine research.