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Fig. 3 | BMC Microbiology

Fig. 3

From: Microbial circadian clocks: host-microbe interplay in diel cycles

Fig. 3

Interactions between host and gut microbiota diel cycles

(A) Abiotic inputs including light-dark cycles and feeding habits entrain the host central clock (the circadian oscillator located in the SCN in the brain). Feeding directly impacts oscillations in gene expression in the peripheral clocks located in the gut and liver. Peripheral clocks are indirectly entrained to light through signals from the SCN. Together the central clock and peripheral clocks regulate the host circadian rhythm. (B) Host immune responses and gut microbiota display daily oscillations in function, magnitude, and activity. These oscillations impact and are influenced by the host circadian rhythm. (C) In the gut, molecules found on resident bacteria (e.g., flagellin and LPS) and microbial metabolites (e.g., BSHs, SCFAs, etc.) interact with host cell receptors. (D) These interactions can activate the host immune system and result in production of cytokines and ultimately inflammation in host tissues or (E) can trigger intestinal epithelial cells to produce antimicrobial peptides. SFB stimulate production of antimicrobial peptides by rhythmic interactions with host tissues, and regularly attach to gut epithelial cells in the morning. Resident microbiota and host cells influence each other in a complex and bidirectional manner (C-E). The behaviors of resident microbiota impact the host immune response and stimulate production of antimicrobial peptides, which ultimately impacts the physiology of the host as well as the species composition and metabolism of the gut microbiota. Created with BioRender.com.

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