An early microbial landscape: inspiring endeavor from the China Space Station Habitation Area Microbiome Program (CHAMP).

China's progressing space program, as evidenced by the formal operation of the China Space Station (CSS), has provided great opportunities for various space missions. Since microbes can present potential risks to human health and the normal operation of spacecraft, the study on space-microorganisms in the CSS is always a matter of urgency. In addition, the knowledge on the interactions between microorganisms, astronauts, and spacecraft equipment will shed light on our understanding of life activities in space and a closed environment. Here, we present the first comprehensive report on the microbial communities aboard the CSS based on the results of the first two survey missions of the CSS Habitation Area Microbiome Program (CHAMP). By combining metagenomic and cultivation methods, we have discovered that, in the early stage of the CSS, microbial communities are dominated by human-associated microbes, with strikingly large differences in both composition and functional diversity compared to those found on the International Space Station (ISS). While the samples from two missions of CHAMP possessed substantial differences in microbial composition, no significant difference in functional diversity was found, although signs of accumulating antibiotic resistance were evident. Meanwhile, strong bacteria co-occurrence was noted within the station's microbiota. At the strain level, environmental isolates from the CSS exhibited numerous genomic mutations compared to those from the Assembly, Integration, and Test (AIT) center, potentially linked to the adaptation to the unique conditions of space. Besides, the intraspecies variation within four high-abundance species suggests possible propagation and residency effects between sampling sites. In summary, this study offers critical insights that not only advance our understanding of space microbiology but also lay the groundwork for effective microbial management in future long-term human space missions.