Extraction and Evaluation of Outer Membrane Vesicles from Two Important Gut Microbiota Members, Bacteroides fragilis and Bacteroides thetaiotaomicron

Document Type : Original Article

Authors

1 .Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran

2 .Cancer Department, Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran;.Laboratory of Experimenta

3 .Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran;4.Microbiology Research Centre, Pasteur Institute of Iran, Tehran, Iran

4 5.Department of Pharmacotherapy, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran

5 6.Medicinal Plants Research Centre, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran

Abstract

Objective
The gastrointestinal tract (GI) is colonized by a complex microbial community of gut microbiota. Bacteroides spp. have significant roles in gut microbiota and they host interactions by various mechanisms, including outer membrane vesicle (OMVs) production. In the present study, we extracted and assessed Bacteroides fragilis (B. fragilis) and Bacteroides thetaiotaomicron (B. thetaiotaomicron) OMVs in order to evaluate their possible utility for in vivo studies.
Materials and Methods
In this experimental study, OMVs extraction was performed using multiple centrifugations and tris-ethylenediaminetetraacetic acid (EDTA)-sodium deoxycholate buffers. Morphology, diameter, protein content, profile, and lipopolysaccharide (LPS) concentrations of the OMVs were assessed by scanning electron microscopy (SEM), nanodrop, Bradford assay, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), and the Limulus Amoebocyte Lysate (LAL) test, respectively. Zeta potential (ζ-P) was also assessed. The viability effect of OMVs was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay in Caco-2 cells.
Results
Spherical OMVs with diameters of 30-110 nm were produced. The OMVs had different protein profiles. The LPS concentrations of the B. fragilis and B. thetaiotaomicron OMVs were 1.80 and 1.68 EU/mL, respectively. ζ-P of the B. fragilis OMVs was -34.2 mV and, for B. thetaiotaomicron. it was -44.7 mV. The viability of Caco-2 cells treated with OMVs was more than 95%.
Conclusion
The endotoxin concentrations of the spherical OMVs from B. fragilis and B. thetaiotaomicron were within the safe limits. Both OMVs had suitable stability in sucrose solution and did not have any cytotoxic effects on human intestinal cells. Based on our results and previous studies, further molecular evaluations can be undertaken to design OMVs as possible agents that promote health properties.

Keywords