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Clean Water in Space: The GULBI Biofilm Experiment

Rocket launching against a cloudy blue sky, emitting bright flames. A small bird is visible in the distance, creating a dynamic scene.
Cygnus CRS-2 NG-23 launch heading to the International Space Station with the GULBI experiment in the payload.

In space, clean water is life. Astronauts rely on advanced filtration, chemical treatment, and recycling systems that reclaim water from everything from humidity to wastewater. Alongside experiments like the SSC crystal growth study, the Cygnus CRS-2 NG-23 (launched on September 14, 2025) mission payload is also carrying the GULBI (Germicidal Ultraviolet Light Biofilm Inhibition) experiment.  This part of the payload sends research that could transform how we keep water safe in space and on Earth.

What’s the problem?

When bacteria stick to surfaces, they form a slimy layer called a biofilm (like the film that builds up inside a water bottle if it goes unwashed). On the ISS, biofilms can form inside water pipes and tanks, making water unsafe to drink and clogging important equipment. Specifically, this experiment aims to study the effects of germicidal UV light on the inhibition of biofilms in water systems using the bacterial pathogen, Pseudomonas aeruginosa (P. aeruginosa) that is present in the International Space Station water systems. 

In hospital-acquired infections, Pseudomonas aeruginosa is a frequent culprit, causing pneumonia, bloodstream, urinary tract, and wound infections, and posing treatment challenges due to its multidrug resistance. It becomes clearer how exploring this bacteria’s properties on the ISS can not only help astronauts but can also translate to Earth applications.  This is another great example of how exploring space, can potentially benefit us all.  On Earth, people usually use chemicals like bleach to kill biofilms. But in space, storing and handling these chemicals is difficult and risky for astronauts.

A closeup view of tube like bacteria.
Pseudomonas aeruginosa SEM — a scanning electron micrograph of P. aeruginosa. The image is from the CDC’s Public Health Image Library.

What’s being tested?

The GULBI experiment is testing a chemical-free solution: special UV light delivered through thin glowing fibers that shine inside the pipes and tanks. The UV light damages bacterial DNA so they can’t form biofilms.


The study is asking two main questions:

  • Does this UV fiber system work in space the same way it does on Earth?

  • Does microgravity make bacteria harder to kill or easier to grow?

Blue laser beam passes vertically through a plastic grid and liquid-filled container, casting a glow. White background, dim lighting.
Electronics setup with various components: a black box labeled "BioServe," a circuit board, and wired devices on a white surface.
NASA Images above: JSC2025E067421 - Biowells, electronics, cooling units, and Plate Habitat (PHAB) are used on International Space Station for the Germicidal Ultraviolet Light Biofilm Inhibition (GULBI) investigation. GULBI examines how microgravity affects the ability of a type of ultraviolet (UV) light to prevent formation of large communities of microbes called biofilms. Image courtesy of Arizona State University.

Applications on Earth

This kind of UV-based disinfection is already being used here on Earth in water treatment plants, hospitals, and HVAC systems to reduce bacterial growth. The fiber-optic method being tested in space could make these systems more efficient and adaptable, especially for smaller, portable, or remote setups.

Why test it in space?

Microgravity provides a unique environment where bacteria can behave differently than on Earth. By testing UV fiber technology under these conditions, scientists can:

  • Develop safer, chemical-free water systems for astronauts on long missions to the Moon and Mars.

  • Learn more about how bacteria adapt under stress, improving biofilm prevention methods on Earth.

  • Strengthen Earth-based UV systems by applying insights gained from extreme space conditions.

Why it matters

If successful, this technology could ensure astronauts have clean, safe water in space without chemicals. At the same time, the research could enhance clean water systems on Earth, supporting sustainability and public health worldwide.


Together with the SSC crystal experiment, GULBI shows how NG-23 is more than just a rocket launch, it’s carrying discoveries that could shape the future of technology, health, and sustainability for everyone back on Earth.

 

 

References

BioServe Space Technologies. (n.d.). Flight history. University of Colorado Boulder. Retrieved September 17, 2025, from https://www.colorado.edu/center/bioserve/flight-history


ISS National Lab. (2025, September 12). ISS National Lab advances research in space with dozens of experiments on next cargo mission. https://issnationallab.org/press-releases/iss-national-lab-advances-research-in-space-with-dozens-of-experiments-on-next-cargo-mission/


NASA. (n.d.). Space Station Research Investigation (ID: 9305). NASA. Retrieved September 17, 2025, from https://www.nasa.gov/mission/station/research-explorer/investigation/?#id=9305


Zhao, Z., Rho, H., Shapiro, N., Ling, L., Perreault, F., Rittmann, B., & Westerhoff, P. (2023). Biofilm inhibition on surfaces by ultraviolet light side-emitted from optical fibres. Nature Water, 1(7), 649–657. https://doi.org/10.1038/s44221-023-00111-7

 

 

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