Gastroenterology

Gastroenterology

Volume 147, Issue 5, November 2014, Pages 1055-1063.e8
Gastroenterology

Original Research
Full Report: Basic and Translational—Alimentary Tract
Correlation Between Intraluminal Oxygen Gradient and Radial Partitioning of Intestinal Microbiota

https://doi.org/10.1053/j.gastro.2014.07.020Get rights and content

Background & Aims

The gut microbiota is a complex and densely populated community in a dynamic environment determined by host physiology. We investigated how intestinal oxygen levels affect the composition of the fecal and mucosally adherent microbiota.

Methods

We used the phosphorescence quenching method and a specially designed intraluminal oxygen probe to dynamically quantify gut luminal oxygen levels in mice. 16S ribosomal RNA gene sequencing was used to characterize the microbiota in intestines of mice exposed to hyperbaric oxygen, human rectal biopsy and mucosal swab samples, and paired human stool samples.

Results

Average Po2 values in the lumen of the cecum were extremely low (<1 mm Hg). In altering oxygenation of mouse intestines, we observed that oxygen diffused from intestinal tissue and established a radial gradient that extended from the tissue interface into the lumen. Increasing tissue oxygenation with hyperbaric oxygen altered the composition of the gut microbiota in mice. In human beings, 16S ribosomal RNA gene analyses showed an increased proportion of oxygen-tolerant organisms of the Proteobacteria and Actinobacteria phyla associated with rectal mucosa, compared with feces. A consortium of asaccharolytic bacteria of the Firmicute and Bacteroidetes phyla, which primarily metabolize peptones and amino acids, was associated primarily with mucus. This could be owing to the presence of proteinaceous substrates provided by mucus and the shedding of the intestinal epithelium.

Conclusions

In an analysis of intestinal microbiota of mice and human beings, we observed a radial gradient of microbes linked to the distribution of oxygen and nutrients provided by host tissue.

Section snippets

Materials and Methods

Molecular oxygen quenches phosphorescence originating from excited triplet electronic states of molecules. The dependence of the phosphorescence lifetime (τ) on the Po2 in the environment throughout the range of biological oxygen concentrations follows the Stern–Volmer model: 1/τ = 1/τ0 + kq × Po2, where τ is the phosphorescence lifetime, and τ0 and kq are probe-specific parameters. By exciting an object containing a probe with a pulse of light and measuring the phosphorescence decay, Po2 in

Oxygen Measurements

The synthetic dendritic phosphorescent probes for tissue oxygen measurements23, 24, 25, 26 do not interact with proteins or other endogenous molecules, and the calibration parameters of these probes remain unchanged in any aqueous environment, ensuring absolute oxygen quantification.27 In the present study, we used one such probe, Oxyphor G4,24 to measure Po2 in the intestinal tissue. The probe was injected into the tail vein in mice, and measurements were performed in reflectance-type geometry

Discussion

Previous studies established that the composition of the gut microbiota differs along the longitudinal axis of the gut. Here, we report that the gut microbiota also is segregated radially and correlated with the radial oxygen gradient and distribution of the tissue-associated mucus, which provides a nutrient source. By using the phosphorescence quenching method, we provide direct evidence that oxygenation of the host influences gut luminal oxygenation. Luminal oxygenation increased after an

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    Conflicts of interest The authors disclose no conflicts.

    Funding Supported by a North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition Fellow to Faculty Transition Award in inflammatory bowel disease research (L.A.); National Institutes of Health grant UH2/3 DK083981 (G.D.W., F.D.B., and J.D.L.); National Institutes of Health grant R01 GM103591 (G.D.W. and S.A.V.); Office of Naval Research grant N000141310613 (S.R.T.); a Molecular Biology and Molecular Pathology and Imaging Cores of the Penn Center for the Molecular Studies in Digestive and Liver Diseases grant (P30 DK050306); and the Joint Penn-Children's Hospital of Philadelphia Center for Digestive, Liver, and Pancreatic Medicine.

    Author names in bold designate shared co-first authorship.

    Authors share co-first authorship.

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