Table 2.
Study characteristics of studies using molecular-based approaches, characteristics are split according to corresponding isolation habitats.
| Study ID | Author (Year) | Origin | Isolation | Length (days) | Sample Size | Age (years) | Sex, % f. | Pre-BMI (kg/m2) | Sampling point | Analysis method | Microbiota classification | Data derivation | Diet | Additional intake |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Subgroup 1: Isolation caused by space missions | ||||||||||||||
| 1 | Garret-Bakelman et al. (25) | USA | Spaceflight | 340 | 1 | 50 | 0 | N.R. | Pr/Du/Po | WMGS (Illumina) | N.R. | Text + graphic | Restricted diet | N.R. |
| 2 | Liu et al. (40) | CHN | Spaceflight | 35 | 2 | N.R. | N.R. | N.R. | Pr/Po | WMGS (Illumina) | N.R. | Text + graphic | Similar with ground life | N.R. |
| 3 | Voorhies et al. (37) | RUS/ USA | Spaceflight | 180–360 | 5 | N.R. | N.R. | N.R. | Pr/Du/Po | 16S rRNA gene (V4 hypervariable region) (Illumina) | OTUs | Text + graphic | N.R. | none |
| Subgroup 2: Isolation caused by spaceflight- or gravity simulators | ||||||||||||||
| 4 | Brereton et al. (58) | RUS | Mars-5001-unit | 520 | 6 | 29–40 | 0 | 25.5 (23.0–31.3) | Du | 16S rRNA gene (V3-V4 hypervariable region) (Illumina) | ESVs | Text + graphic | Tinned foods similar to those used in ISS, by RUS/EUR/KOR/CHN firms, 15.1% protein, 33.4% fat, and 51.2% CH | Streptococcus thermophilus via yoghurt |
| 5 | Turroni et al. (59) | 31.8 (27–38) | Pr/Du/Po | OTUs | Text | N.R. | ||||||||
| 6 | Mardanov et al. (44) | 510 | 5 | 28–38 | N.R. | N.R. | Pr/Du/Po | 16S rRNA gene (V3-V5 hypervariable region) (Pyrosequencing) | N.R. | Text + graphic | Enterococcus faecium, Eubikor, Vitaflor | |||
| 7 | Hao et al. (60) | CHN | Lunar Palace 1 (BLSS) | 79–105 | 3 | 27–32 | 66. 6 | 21.3 ± 3 (19–24) |
Pr/Du/Po | 16S rRNA gene (V3-V4 hypervariable region) (Illumina) | OTUs | Text | Predesigned high-plant and high-fibre diet | N.R. |
| 8 | Li et al. (46) | N.R. | Graphic | |||||||||||
| 9 | Meng et al. (61) | CHN | Lunar Palace 1 (BLSS) | 63 | 4 | 26 | 50 | N.R. | Du | WMGS (Illumina) | N.R. | Text | NASA astronauts’ dietary standards | N.R. |
| 10 | Chen et al. (62) | CHN | BLSS | 60 | 4 | 23–27 | 50 | 18.5–22.9 | Pr/Du/Po | WMGS (BGI-SEQ500 platform) | N.R. | Text | ↑ CH, ↓ fat | N.R. |
| 11 | Dong et al. (63) | CHN | CELSS | 180 | 4 | 26–36 | 25 | 18.6–24.6 | Pr/Du | 16S rRNA gene (V3-V4 hypervariable region) (Illumina) | OTUs | Text + graphic | in accordance with customs of Chinese population, 3 meals/d, main composition: CH, protein, fat, fiber | N.R. |
| Subgroup 3: Isolation in a natural, earth-bound habitat | ||||||||||||||
| 12 | Jin et al. (64) | JPN | Antartica | 60 | 6 | 37–55 | 0 | N.R. | Pr/Du/Po | 16S rDNA (T-RFLP, rtPCR) | OTUs | Text | N.R. | N.R. |
| 13 | Zhang et al. (65) | CHN | Sea voyage | 30 | 42 | 25 ± 4.2 | 0 | 22.3 ± 2.7 | Du | WMGS (Illumina) | N.R. | Graphic | Controlled, similar diet, Buffet style, min. 2 staple foods/d, 5 entrées/d, 2–3 fruit/d | Lactobacillus casei Zhang, Lactobacillus plantarumP-8, Lactobacillus rhamnosus M9, Bifidobacterium lactis V9, Bifidobacterium lactis M8 |
| 40 | no | |||||||||||||
“Isolation”: Isolated and confined extreme environments. “Length”: length of the isolation intervention, no pre/post surveys are considered. The sampling times are either before the start of the intervention (“Pre”), during the isolation itself (“During”), after the isolation (“Post”), or a combination of more than one of these times. “Additional intake”: intake of pro−/pre−/antibiotics during the isolation period. Control groups are not shown.
1Project to simulate a manned flight to Mars. 16S rDNA, 16S ribosomal Deoxyribonucleic acid; 16S rRNA, 16S ribosomal Ribonucleic acid; BLSS, Bioregenerative life support systems; CELSS, Controlled (or closed) ecological life-support systems; CH, carbohydrates; CHN, China; d, day; f, female; Du, During; JPN, Japan; N.R., not reported; Po, Post; Pr, Pre; rtPCR, reverse transcription polymerase chain reaction; RUS, Russia; T-RFLP, Terminal restriction fragment length polymorphism; USA, United States of America; WMGS, Whole metagenome shotgun sequencing. BMI, Body Mass Index; OTU, Operational taxonomic unit; ESV, exact sequence variants; KOR, Korea; EUR, Europe; NASA, National Aeronautics and Space Administration; ISS, International Space Station.