On-orbit Microbial Succession Patterns Of The China Space Station During The Construction Period
Background: The China Space Station (CSS) modules feature many areas that are difficult to clean and thus susceptible to microbial outbreaks. A new sampling method utilizing an equivalent material sheet was applied to characterize the diversity of microbes that accumulated in inaccessible areas in orbit on the CSS. Equivalent material sheet is a membrane made of the same material as the wall of the module.
Results: Fifty samples were collected from interior surfaces (work, sleeping, and sanitary areas) of the Tianhe core module and the Wentian and Mengtian experimental modules, covering three flights by the Shenzhou (SZ)-12 to SZ-14 astronaut crews from 2021 to 2022. The numbers of culturable bacteria and fungi that accumulated during the on-orbit periods of each flight ranged from 0 to 2.83 × 109 colony-forming units/100 cm2.
The number of bacteria detected by quantitative PCR (qPCR) ranged from 1.24 × 105 to 2.59 × 109 rRNA gene copies/100 cm2, with an average viability of 65.08%. A total of 103 bacterial strains and 27 fungal strains were cultured and isolated.
The dominant culturable microorganisms were mainly from the genera Bacillus, Staphylococcus, Aspergillus, Cladosporium, and Penicillium. High-throughput sequencing results showed that the predominant bacteria were Pseudomonas, Stenotrophomonas, Methylobacterium-Methylorubrum, Sphingomonas, Bacillus, Staphylococcus, and Nocardiopsis. The microbial diversity in each module varied significantly with sampling time and sampling area.
In the early stage of CSS construction with the SZ-12 crew, the microbial species evenness in the modules was high; later, with the SZ-13 crew, Pseudomonas began to appear as the dominant microorganism. More than half (58.80%) of the bacteria on module surfaces originated from the human skin and oral environments. Lactobacillus was present in all areas of the three modules at all sampling times.
The biomarker bacteria Stenotrophomonas sp., isolated from the work area in the Tianhe core module, are typically derived from plants. SourceTracker analysis indicated that most of the microbes in the orbiting CSS came from human bodies, and that microbial diversity was significantly altered with each crew change.
Conclusion: Future efforts at microbial prevention and control on orbit should emphasize the human and plant origins of microbes. Information on the microbial diversity in the condensate zone could be useful to guide the development of new strategies to prevent and control microbes during space flight. Video Abstract.
Phylogenetic tree of culturable fungi. Individual microorganisms are color-coded by taxonomic family level, with 10 families in total. The end of each strain name is labeled with the region of the space station module from which the strain was isolated. There were 11 subgroups: SZ-12 Work area, 12 Sleeping area, 13 Work area, 13 Sleeping area, 13 Sanitary area, 14-TH Work area, 14-TH Sleeping area, 14-TH Sanitary area, 14-WT Work area, 14-WT Sleeping area, and 14-MT Work area. Phylogenetic tree constructed using MEGA software (Version 11.0.13), with the bootstrap replication number set to 1000 – Microbiome via PubMed
Phylogenetic tree of culturable bacteria. Individual microorganisms are color-coded by taxonomic family, with 18 families in total. The end of each strain name is labeled with the region of the space station module from which the strain was isolated. There were 11 subgroups: SZ-12 Work area, 12 Sleeping area, 13 Work area, 13 Sleeping area, 13 Sanitary area, 14-TH Work area, 14-TH Sleeping area, 14-TH Sanitary area, 14-WT Work area, 14-WT Sleeping area, and 14-MT Work area. Phylogenetic tree constructed using MEGA software (Version 11.0.13), with the bootstrap replication number set to 1000. – Microbiome via PubMed
IMAGE
Schematic illustration of the distribution of sampling sites. The sampling sites for the SZ-12, SZ-13, and SZ-14 flights are labeled as follows: red dots for SZ-12 (with red pentagrams indicating the sampling sites in the condensate region), blue dots for SZ-13, and green dots for SZ-14 – Microbiome via PubMed
On-orbit microbial succession patterns of the China Space Station during the construction period, Microbiome. 2025 Feb 5;13(1):73. doi: 10.1186/s40168-024-02025-2. via PubMed
Astrobiology,
Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 
