GC-MS Detection of Microbes in Spacecraft Water

As humans venture further into space, beyond the reach of regular supply missions, having a reliable way to recycle and purify water becomes essential. The problem with current methods of detecting harmful microbes in spacecraft water is that they require astronauts to be present and use up limited supplies, making them useless when no one is on board. One promising alternative is to simply sample the air above the water and check for specific gases that microbes give off, which can be done remotely and without any special preparation. A recent paper in the journal Analyst¹ presented the findings of researchers who used gas chromatography-mass spectrometry (GC-MS) to analyze the headspace above cultures of bacteria returned from the International Space Station.

Why is Monitoring Microbial Contamination in Spacecraft Water Systems Important?

Having access to clean water is critical for keeping both the crew and the equipment on a spacecraft healthy and functioning. Clean water is needed for drinking, personal hygiene, producing oxygen, flushing toilets, and supporting experiments. On the International Space Station (ISS), clean water is produced by the Water Recovery System, which is made up of two main components that work together to treat wastewater. This wastewater comes primarily from a combination of moisture collected from the air and processed urine, though other sources of water may also be added to the mix.²

What is the Need for New, Less Crew-Dependent Methods of Detecting Microbes in Spacecraft Water Systems?

Cutting-edge gene sequencing technology has been developed and tested on the ISS over the past decade, initially to analyze surfaces on the station, and more recently to examine water samples.^3,4 The researchers state that their work marked the first time microbes were ever identified in space, collected directly from spacecraft surfaces. While these techniques have proven effective and are still being improved, they require a significant amount of the crew's time and attention. As NASA looks ahead to future deep space missions (which may involve periods where the spacecraft is empty or in a low-activity standby mode but will likely still require some form of water treatment), it becomes important to explore other monitoring methods that don't rely as heavily on the crew. Ideally, these methods would be able to give astronauts a general sense of whether microbes are present in the water system before they even re-enter the spacecraft or habitat, without requiring hands-on testing.^5-8

Can the Gases Released by Bacteria Be Used to Detect Unwanted Microbial Growth in Spacecraft Water Systems?

For this research, three types of bacteria — Ralstonia pickettii, Burkholderia contaminans, and Klebsiella aerogenes — were grown in a laboratory, and the gases released by each were analyzed using GC-MS. Several compounds were found that were unique to each individual species, but one compound in particular, dimethyl disulfide, showed up consistently across all three species and in every test condition. The genetic makeup of each bacterial strain was also examined, and genes were found that could be responsible for producing dimethyl disulfide. This supported the idea that all three bacteria naturally produce this compound as a waste product when breaking down a specific amino acid called methionine. Overall, these findings suggest that dimethyl disulfide could be a reliable chemical signal to look for when trying to detect unwanted bacterial growth in the water recovery systems of future spacecraft.¹

“The results shown here,” state the authors of the paper,¹ “suggest that the use of MS-based techniques for headspace VOC analysis is a promising avenue for the detection of these common spacecraft bacteria in spaceflight wastewater.”

The researchers point out, however, that more research is needed on the gases produced by bacteria under different conditions to figure out whether this detection method could work in other areas of a spacecraft. Furthermore, it would be helpful to study more types of bacteria, as well as situations where multiple bacteria species are living together. Also, while the timeframes in which key gases were detected were good enough for the purposes of this study, more frequent monitoring could help pinpoint more precisely when bacteria become detectable. Lastly, a closer look at how the various components of the artificial wastewater might interfere with gas collection and analysis would be important for confirming that this method works reliably in such a complex environment.¹

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References

1. Kingsley, S.; Nguyen, H. N.; Knopp, A. N. et al. Identification of Volatile Organic Compound Markers for Bacterial Growth in Spacecraft Wastewater. Analyst 2026. DOI: 10.1039/d6an00060f
2. Status of ISS Water Management and Recovery. 53^rd International Conference on Environmental Systems; J. Williamson, J. P. Wilson, and H. Luong,Eds.; ICES, 2024.
3. Stahl-Rommel, S.; Jain, M.; Nguyen, H. N. et al. Real-Time Culture-Independent Microbial Profiling Onboard the International Space Station Using Nanopore Sequencing. Genes (Basel) 2021, 12 (1), 106. DOI: 10.3390/genes12010106
4. Mena, C. G.; Stahl-Rommel, S.; Nguyen, H. N. et al. Redefining Spaceflight Microbiology: The Evolution of In Situ Nanopore Sequencing for Microbial Monitoring of Crewed Spacecraft; The 53rd International Conference on Environmental Systems, 2024.
5. Burton, A. S.; Stahl, S. E.; John, K. K. et al. Off Earth Identification of Bacterial Populations Using 16S rDNA Nanopore Sequencing. Genes (Basel) 2020, 11 (1), 76. DOI: 10.3390/genes11010076
6. NASA Environmental Control and Life Support Technology Development for Exploration: 2021 to 2022 Overview. 51^st International Conference on Environmental Systems, ed. J. L. Broyan, J. L.; M. McKinley, M.; I. Stambaugh, I. et al. Eds.; ICES, 2022.
7. Eshima S. P.; Nabity, J. A. et al. Impact of Dormancy on ECLSS Design and Operation: A Review, Acta Astronaut. 2024, 223, 304-315. DOI: 10.1016/j.actaastro.2024.06.004
8. Fuller, S.; Lehnhardt, E.; Zaid, C. et al. Gateway Program Status and Overview, J. Space Saf. Eng. 2022, 9, 625-628. DOI: 10.1016/j.jsse.2022.07.008