Abstract
Background: In the past, many studies suggested a crucial role for dysbiosis of the gut microbiota in the etiology of Crohn’s disease (CD). However, despite being important players in host–bacteria interaction, the role of bacterial membrane vesicles (MV) has been largely overlooked in the pathogenesis of CD. In this study, we addressed the composition of the bacterial and MV composition in fecal samples of CD patients and compared this to the composition in healthy individuals. Methods: Fecal samples from six healthy subjects (HC) in addition to twelve CD patients (six active, six remission) were analyzed in this study. Fecal bacterial membrane vesicles (fMVs) were isolated by a combination of ultrafiltration and size exclusion chromatography. DNA was obtained from the fMV fraction, the pellet of dissolved feces as bacterial DNA (bDNA), or directly from feces as fecal DNA (fDNA). The fMVs were characterized by nanoparticle tracking analysis and cryo-electron microscopy. Amplicon sequencing of 16s rRNA V4 hypervariable gene regions was conducted to assess microbial composition of all fractions. Results: Beta-diversity analysis showed that the microbial community structure of the fMVs was significantly different from the microbial profiles of the fDNA and bDNA. However, no differences were observed in microbial composition between fDNA and bDNA. The microbial richness of fMVs was significantly decreased in CD patients compared to HC, and even lower in active patients. Profiling of fDNA and bDNA demonstrated that Firmicutes was the most dominant phylum in these fractions, while in fMVs Bacteroidetes was dominant. In fMV, several families and genera belonging to Firmicutes and Proteobacteria were significantly altered in CD patients when compared to HC. Conclusion: The microbial alterations of MVs in CD patients particularly in Firmicutes and Proteobacteria suggest a possible role of MVs in host-microbe symbiosis and induction or progression of inflammation in CD pathogenesis. Yet, the exact role for these fMV in the pathogenesis of the disease needs to be elucidated in future studies.
Highlights
Inflammatory bowel disease (IBD) comprises Crohn’s disease (CD) and ulcerative colitis
The graphs represent the relative differences in healthy controls. DNA obtained directly from fecal samples, DNA obtained from pellet of dissolved feces in PBS–bacteria directly from(MV-DNA)
The abundance of Sutterellaceae was significantly increased in patients with active disease, and at the genus level a significant trend could be observed with lowest levels of Suterella among healthy subjects (HC), intermediate levels in Re-CD and the highest levels among Ac-CD
Summary
Inflammatory bowel disease (IBD) comprises Crohn’s disease (CD) and ulcerative colitis. MVs can contain lipids, outer membrane proteins, nucleic acids, ATPs, and cytoplasmic and inner membranes As a result, they play a crucial role in bacterial survival, nutrient sensing, carrying virulence factors, modulation of host immune function, and killing competing bacteria [5,6,7,8,9,10]. Many studies suggested a crucial role for dysbiosis of the gut microbiota in the etiology of Crohn’s disease (CD). Results: Beta-diversity analysis showed that the microbial community structure of the fMVs was significantly different from the microbial profiles of the fDNA and bDNA. Conclusion: The microbial alterations of MVs in CD patients in Firmicutes and Proteobacteria suggest a possible role of MVs in host-microbe symbiosis and induction or progression of inflammation in CD pathogenesis. The exact role for these fMV in the pathogenesis of the disease needs to be elucidated in future studies
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