Simulated manned Mars exploration: effects of dietary and diurnal cycle variations on the gut microbiome of crew members in a controlled ecological life support system

Hai-Sheng Dong; Pu Chen; Yan-Bo Yu; Peng Zang; Zhao Wei

doi:10.7717/peerj.7762

Simulated manned Mars exploration: effects of dietary and diurnal cycle variations on the gut microbiome of crew members in a controlled ecological life support system

PeerJ. 2019 Sep 26:7:e7762. doi: 10.7717/peerj.7762. eCollection 2019.

Authors

Hai-Sheng Dong^{1

2}, Pu Chen², Yan-Bo Yu³, Peng Zang², Zhao Wei²

Affiliations

¹ Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, MOE Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology, Tsinghua University, Beijing, China.
² State Key Lab of Space Medicine Fundamentals and Application, Key Laboratory of Space Nutrition and Food Engineering, China Astronaut Research and Training Center, Beijing, China.
³ SPACEnter Space Science and Technology Institute, Shenzhen, China.

Abstract

Background: Changes in gut microbiome are closely related to dietary and environment variations, and diurnal circle interventions impact on human metabolism and the microbiome. Changes in human gut microbiome and serum biochemical parameters during long-term isolation in a controlled ecological life support system (CELSS) are of great significance for maintaining the health of crewmembers. The Green Star 180 project performed an integrated study involving a four-person, 180-day duration assessment in a CELSS, during which variations in gut microbiome and the concentration of serum 25-hydroxyvitamin D, α-tocopherol, retinol and folic acid from the crewmembers were determined.

Results: Energy intake and body mass index decreased during the experiment. A trade-off between Firmicutes and Bacteroidetes during the study period was observed. Dynamic variations in the two dominant genus Bacteroides and Prevotella indicated a variation of enterotypes. Both the evenness and richness of the fecal microbiome decreased during the isolation in the CELSS. Transition of diurnal circle from Earth to Mars increased the abundance of Fusobacteria phylum and decreased alpha diversity of the fecal microbiome. The levels of serum 25-hydroxyvitamin D in the CELSS were significantly lower than those outside the CELSS.

Conclusions: The unique isolation process in the CELSS led to a loss of alpha diversity and a transition of enterotypes between Bacteroides and Prevotella. Attention should therefore be paid to the transition of the diurnal circle and its effects on the gut microbiome during manned Mars explorations. In particular, serum 25-hydroxyvitamin D levels require monitoring under artificial light environments and during long-term space flight. Large-scale studies are required to further consolidate our findings.

Keywords: 16S gene sequencing; 25-hydroxyvitamin D; Alpha diversity; Biomarker screening; Controlled Ecological Life Support System Environment; Core microbiome; Crewmembers; Longitudinal variation; Manned Mars exploration.

Grants and funding

This work was funded by the National Natural Science Foundation of China (NO. 21435002, 21621003) and the Shenzhen Science and Technology Plan Project (JCYJ20170818100846805, JCYJ20180305163647462). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.