“…Furthermore, the symbiosis between the host and gut microbiota plays a critical role in maintaining the homeostasis of the host and dysbiosis of microbiota, which accounts for immune dysregulation and an impaired digestive system and metabolism (Knight and Girling, 2003;Thaiss et al, 2014). Symbiotic microbiota functions to bridge circadian rhythms with diverse effects, including development immunity and metabolism (Brooks et al, 2021;Kuang et al, 2019;Thaiss et al, 2014;Ma et al, 2019;Collado et al, 2018). Much evidence has revealed that space environment factors or analog conditions (e.g., microgravity, radiation, low fluid shear, and diet) cause altered composition of gut microbiota (Siddiqui et al, 2021;Acres et al, 2021;Cervantes and Hong, 2016;Saei and Barzegari et al, 2012;Li et al, 2015;Jiang et al, 2019).…”