(A) Schematic showing sampling times for luminal and mucosal-adherent communities.

(B) SEM images showing diurnal fluctuations in epithelial colonization by bacteria. Images are representative of ten randomly chosen views per mouse.

(C) Diurnal fluctuations in the number of bacteria attached to colonic epithelium over two dark-light cycles as determined by bacterial qPCR of adherent communities.

(D) Relative taxonomic composition of mucosal-adherent bacteria over the course of two dark-light cycles.

(E) Principal coordinate analysis (PCoA) of mucosal-adherent bacteria over the course of two dark-light cycles.

(F) Epithelial-adherent operational taxonomic units (OTUs) showing diurnal oscillations in absolute abundance. Fluctuation amplitudes are depicted. Dashed line indicates q < 0.1.

(G) Example of a bacterial species showing fluctuating absolute numbers in mucosal-adherent communities.

(H and I) Dot plot (H) and heatmap (I) of diurnal gene abundance oscillations in mucosal commensal bacteria. Genes with p < 0.05 and q < 0.1 are shown.

Data are expressed as mean ± SEM and are representative of two independent experiments with n = 45 (A–G) or n = 18 mice (H and I) mice. JTK_cycle was used to calculate p and q values.