The gut microbial alterataion in KUHIMM

Background: Fecal lipopolysaccharide (LPS) levels, as a potent elements to explain a strong correlation between the gut microbiota and diseases progression, has attracted attention. However, how specific gut bacteria contributes to fecal LPS levels and its underling mechanisms remains to be determined. Methods: We used our clinical datasets (n = 92) to rank the gut microbiota in genus levels according to contribution toward fecal LPS levels. The gut microbiota was determined by 16S ribosomal RNA gene sequencing. Biological activity (endotoxicity) of LPS was assessed by the limulus amebocyte lysate (LAL) tests, cytokine secretion from RAW cells, and survival rate after injected to mice intraperitoneally. Bacterial LPS extraction was performed by hot phenol-water method. Fecal samples were fermented in a single-batch fermentation system, called KUHIMM. Findings: The genus Bacteroides ranked in the first contributor toward fecal LPS levels. Fecal LPS levels in the population with Bacteroides dominant were significantly lower and negatively correlated with the abundance of Bacteroides. Bacteroides-LPS showed drastically lower endotoxin units measured by LAL tests, and reduced pro-inflammatory cytokine production compared to E.coli-LPS. Furthermore, Bacteroides-LPS did not induce sepsis in mice, while same dose of E.coli-LPS did. Finally, the Bacteroides abundance were significantly increased in the human gut microbiota after Bacteroides species were supplemented to fecal samples in KUHIMM.