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

Area of Science:

• Spacecraft microbial contamination assessment
• Astrobiology and space exploration hygiene
• Surface microbiology on extraterrestrial missions

Background:

• Quantifying microbial load on spacecraft is essential for mission safety and planetary protection.
• Previous studies identified high Bacillus sp. abundance on China's Space Station interior surfaces.
• Low-biomass metal surfaces present unique challenges for microbial detection.

Purpose of the Study:

• To identify the most accurate methods for quantifying microbial load on low-biomass metal surfaces relevant to China's Space Station.
• To compare the efficacy of four common analytical approaches: contact plate, spread plate, quantitative PCR, and BacLight™.
• To establish optimal sampling and processing methodologies for microbial enumeration in space station environments.

Main Methods:

• Utilized four common analytical methods: contact plate, spread plate, quantitative PCR, and BacLight™.
• Contaminated metal surfaces with Bacillus sp. TJ 1-1 at levels ranging from 10^2 to 10^9 cells/100 cm^2.
• Evaluated methods using a standardized sampling area of 121 cm^2.

Main Results:

• For low contamination levels (10^2 cells/100 cm^2), the contact plate method was most convenient and reliable.
• For higher contamination levels (≥10^3 cells/100 cm^2), the BacLight™ method was most reliable for detecting viable cells.
• A sampling area of 121 cm^2 was determined to be most suitable for analyzing metal surfaces in space station interiors.

Conclusions:

• The choice of microbial quantification method depends on the expected contamination level.
• The BacLight™ method is recommended for reliable detection of viable microbes at higher contamination levels on space station surfaces.
• Standardized sampling areas are critical for accurate microbial assessment of low-biomass spacecraft surfaces.