Longitudinal analysis of stowaway microorganisms aboard modules and cargo spacecraft of the Chinese Space Station

Although microbial contamination in crewed spacecraft is well studied, quantitative assessment of microorganisms from spacecraft structures and cargo remains overlooked. Here, we investigate 165 microbial samples collected from five critical environments of China Space Station (CSS) missions undertaken in 2016-2024: ground assembly, cargo loading, crewed simulation cabin, test cabin, and on-orbit. The investigation aims to elucidate the impact of cargo- and cabin-derived microorganisms on the CSS microbial community while characterizing the station's unique microbial profile.

The calculation results based on the microbial source tracking model revealed that the proportion of cabin-source microbes peaked during initial construction (14.02%) but declined after deployment, whereas cargo-source microbes reached 36.89%. The top three persistent microbial genera in orbit from both sources were Staphylococcus, Acinetobacter, and Corynebacterium. High-abundance CSS microorganisms in the orbital environment are commonly found in both humans and plants, and the few cabin- or cargo-derived microorganisms that entered the interior differed markedly from high-abundance microorganisms found in terrestrial environments. Cargo storage areas and controlled cleanrooms posed a high risk of microbial transfer into orbit, necessitating stricter sterilization measures.

These findings systematically characterize, for the first time, the dynamic patterns of structural/cargo-borne microbial contamination during CSS's early phases, providing critical data for biosecurity protocols of long-duration missions. Video Abstract.