Relationship between the Gut Microbiome and Energy/Nutrient Intake in a Confined Bioregenerative Life Support System

Abstract

Recent studies have suggested that the gut microbiome is modified in space analogs and that human health can be affected during actual spaceflight. However, the relationship between the gut microbiome and dietary intake in simulator subjects and astronauts remains unclear. Bioregenerative life support systems (BLSSs) are confined and self-sufficient ecosystems that enable exploration of this issue. Here, we correlate changes in gut microbes to the nutrient types present in controlled diets within subjects cohabitating in a BLSS. A metagenome-wide association study (MWAS) was performed on 55 shotgun-sequenced fecal samples longitudinally obtained from healthy Chinese subjects (n = 4 in total, n = 2 per sex) subjected to a 60-day BLSS stay and a specialized diet. Each food item was categorized based on nutrient type according to the Chinese Food Ingredients List (https://wenku.baidu.com/view/3f2b628488eb172ded630b1c59eef8c75fbf9514.html?from=search). The physical parameters of each subject fluctuated within normal medical ranges. Sex- and individual-specific differences and a trend of individual convergence of the gut microbiome in the BLSS were observed. Depletion of bacterial taxa such as Faecalibacterium prausnitzii, Bifidobacterium longum, and Escherichia coli and functional modules such as short-chain fatty acid (SCFA) production, as well as an increase in an unidentified Lachnospiraceae and glutamate/tryptophan synthesis, were observed in the BLSS. Correlation analysis showed that these compositional and functional changes were associated with energy/nutrient intake during the BLSS stay. Our findings suggest that the gut microbiota is a useful indicator for monitoring health and that individual nutritive diets should be considered according to sex and individual differences in simulations or in spaceflight. IMPORTANCE The gut microbiome shows individual specificity and is affected by sex, environment, and diet; gut microbiome imbalance is related to cancer, cardiovascular diseases, and autoimmune diseases. Astronauts are faced with a challenging environment and limited diet in outer space. Recent studies indicate that the gut microbiome is altered in space simulators and space, but what happens to intestinal microorganisms when astronauts cohabitate in a self-sufficient ecosystem in which they plant and cook food is unclear. Bioregenerative life support systems (BLSSs) are ideal devices to investigate the above issues because they are closed and self-sufficient. Four healthy Chinese subjects cohabitated in a confined BLSS for 60 days, during which their physical parameters and energy/nutrient intake were recorded. We performed a metagenome-wide association study (MWAS) on 55 shotgun-sequenced fecal samples longitudinally obtained from the subjects. Alterations occurred in the gut microbial composition and function, and their relationships with energy/nutrient intake were explored.

Gut Microbiome and Space Travelers’ Health: State of the Art and Possible Pro/Prebiotic Strategies for Long-Term Space Missions

“…A parallel experiment, MICHA (MIcrobial ecology of Confined Habitats and humAn health), has instead drawn attention to the microbiology of the environments where space travelers dwell, identifying areas with human activity as hotspots for dispersal and accumulation of crew's microorganisms, especially of potential pathogenic, stress-tolerant or mobile element-bearing microbes (Schwendner et al, 2017). More recently, ground-based space simulations have provided intriguing (although not entirely unequivocal) insights into the possibility of maintaining a eubiotic gut microbiome layout (poor in potential pathobionts while rich in health-promoting SCFA producers) through a bioregenerative life-support system (BLSS), i.e., a confined, selfsustained artificial ecosystem to biologically regenerate O 2 , food, water and other basic living necessities (Hao et al, 2018;Chen et al, 2020). In short, the crewmembers followed a fixed schedule that included contact with plants for several hours a day and a high-plant high-fiber diet.…”

“…More recently, ground-based space simulations have provided intriguing (although not entirely unequivocal) insights into the possibility of maintaining a eubiotic gut microbiome layout (poor in potential pathobionts while rich in health-promoting SCFA producers) through a bioregenerative life-support system (BLSS), i.e., a confined, self-sustained artificial ecosystem to biologically regenerate O 2 , food, water and other basic living necessities ( Hao et al, 2018 ; Chen et al, 2020 ). In short, the crewmembers followed a fixed schedule that included contact with plants for several hours a day and a high-plant high-fiber diet.…”

Human Health during Space Travel: State-of-the-Art Review

“…Gut microbiota dysbiosis [2] Probiotics, synthetic peptides, synthetic biology [35][36][37][38] Acute appendicitis and cholecystitis Inflight medical management or minimally invasive procedures (e.g., ultrasound guided percutaneous drainage) of traditionally "surgical" conditions. [39] Alternatively, can consider prophylactic minimally invasive surgery prior to prolonged space flight in at-risk individuals [40] Cardiovascular Orthostatic intolerance [41] Regular exercise training and adequate hydration prior to landing Cardiac myocyte atrophy [42] Restores back to baseline after returning from spaceflight Ophthalmology Spaceflight-Associated Neuro-Ocular Syndrome (SANS) [43] The lower body negative pressure device has been proposed as a countermeasure but is currently unproven…”

“…Hematology Acute hematopoietic effects [7] Shielding [7] Space-related hemolytic anemia [50,51] Screening and monitoring for hemolysis Neurology Neuro-degenerative disorders and central nervous system changes [52][53][54][55][56] Adaptive visuo-motor training, active sensory feedback to guide task performance, galvanic vestibular stimulation (GVS) Gastroenterology Gut microbiota dysbiosis [2] Probiotics, synthetic peptides, synthetic biology [35][36][37][38] Cardiovascular Accelerated atherosclerosis [3,4,[57][58][59][60] Shielding [7] Ophthalmology Radiation-induced cataract [61,62] No specific countermeasures exist Pulmonology Lung adenocarcinomas and squamous cell carcinomas [63] Shielding [7] Dermatology Melanoma and non-melanoma skin cancers [44] Inflight telediagnostic system…”

Microbiomes of air dust collected during the ground-based closed bioregenerative life support experiment "Lunar Palace 365"

“…In this setting, air represents a vehicle for the movement of microbes from one habitat to another. While there have been several studies of the microbial communities present on humans [ 31 , 32 ] and plants [ 33 , 34 ], few studies have attempted to characterize the airborne microflora in a BLSS. Here, we present the results of our study of the microbial air succession of Lunar Palace 365, which was carried out by monitoring the bacterial air flora in different locations when different groups resided in the habitat.…”