Evaluating Quantitative Measures of Microbial Contamination from China's Spacecraft Materials

Microbiome in a ground-based analog cabin of China Space Station during a 50-day human occupation

Dead-corner areas in space station that untouched by the clean-up campaign often experience microorganisms outbreaks, but the microbiome of these areas has never been studied. In this study, the microbiome in a ground-based analog ``Tianhe'' core module of China Space Station was first investigated during a 50-day three-crew occupation. Dead-corner areas were receiving attention by adopting a new sampling method. Results indicate that the astronauts occupation did not affect the dominant bacteria community, but affected a small proportion. Due to the frequent activity of astronauts in the work and sleep areas, the biomarkers in these two areas are common human skin surface and gut microorganisms, respectively. For areas that astronaut rarely visits, the biomarkers in which are common environmental microbial groups. Fluorescence counting showed that 70.12-84.78% of bacteria were alive, with a quantity of 104-105 cells/100 cm2. With the occupation time extension, the number of microorganisms increased. At the same sampling time, there was no significant bioburden difference in various locations. The cultivable bioburden ranged from 101 to 104 colony forming unit (CFU)/100 cm2, which are the following eight genera Penicillium, Microsphaeropsis, Stachybotrys, Humicola, Cladosporium, Bacillus, Planomicrobium, and Acinetobacter. Chryseomicrobium genus may be a key focus for future microbial prevention and control work.

Evaluation of Decontamination Potential of Wet Wipes Against Microbial Contamination of Chinese Spacecraft Materials

Abstract There are many kinds of microorganisms that inhabit the environment of manned space stations. Wet wipes are a common tool used in space stations to clean and reduce microorganisms on surfaces. Here, we compared the performance of five types of wipes used by the Chinese Space Station (CSS) on orbit before 2021 in terms of microbial decontamination. In previous studies, we found that Bacillus sp. TJ-1-1 and Staphylococcus sp. HN-5 were the most abundant microorganisms in the assembly environment of the CSS. In this study, we used these two bacteria to build different microbial load models to represent the occurrence and non-occurrence of microbial outbreaks in the on-orbit CSS. The results show that the number of microorganisms that can be removed when wiping the surface with high microbial load by wet wipes was higher than that when wiping the surface with low microbial load. For on-orbit daily cleaning and keeping the microbial population within the regulation concentration range, it is suitable to use two pure water wipes per 100 cm2. When the number of microorganisms increases to a degree where astronauts can see the colonies with their naked eyes, the best way to eliminate the problem is to wipe them thoroughly and repeatedly with at least four quaternary ammonium-based wipes every 100 cm2.