The invisible world of microbes threatens to clog humanity's path to the stars, but scientists are fighting back with clever new strategies.
Imagine a stubborn, slimy film coating the inside of your water bottle—now picture that same gunk clogging critical valves 250 miles above Earth on the International Space Station. This isn't science fiction; it's the ongoing battle against biofilms in space, and the solutions scientists are developing might just protect future missions to Mars and beyond while improving water systems back on Earth.
Biofilms are structured communities of microorganisms—bacteria, fungi, and more—that adhere to surfaces and embed themselves in a self-produced matrix of slimy extracellular polymers. Think of the plaque on your teeth or the slippery film on rocks in a stream. These microbial cities are everywhere, but in the confined, water-recycling systems of spacecraft, they transform from mere nuisances into genuine threats.
Visualization of biofilm formation and structure
In space, these biofilms have already demonstrated their destructive potential by clogging valves in the International Space Station's water recovery system, necessitating part replacements and threatening system failures 1 7 . As we plan for longer missions beyond Earth's orbit, where resupplying spare parts becomes impractical, controlling these microbial communities becomes critical for both astronaut safety and mission success.
Structured colonies of bacteria, fungi, and other microorganisms embedded in a protective matrix.
Self-produced extracellular polymeric substance (EPS) that shields microbes from threats.
The Water Recovery System on the International Space Station represents one of humanity's most remarkable engineering achievements—recycling wastewater from human urine and recovered atmospheric humidity into clean, drinkable water. But this life-sustaining closed-loop system paradoxically creates the perfect breeding ground for biofilms.
These systems are continually inoculated with microorganisms primarily arising from the space crew's microbiome. In the warm, moist environment of the ISS, "anywhere there is any moisture, biofilms will grow on surfaces," notes Paul Westerhoff, a Regents Professor at Arizona State University leading research on biofilm prevention 8 .
The problem extends beyond mere inconvenience. Biofilms can:
As Robert McLean, a Texas State University Regents Professor who focuses on biofilms, explains: "While such emergency measures can be done on the ISS, travel to the moon or even Mars does not allow for replacement items to be sent from Earth or crew evacuation in an extreme situation" 8 .
A groundbreaking study led by Dr. Madelyn Mettler and Dr. Brent Peyton from Montana State University's Center for Biofilm Engineering has tested a three-pronged strategy to combat space biofilms. Their research, published in Gravitational and Space Research, represents a significant leap forward in biofilm control for spacecraft water systems 1 2 .
The researchers applied Sher-Loxane® 800, a commercially available protective coating, to surfaces. These coatings create a surface that microorganisms find difficult to adhere to, essentially making the walls of water systems "slippery" to biofilm formation.
Biofilms need food to grow. By removing phosphorus—a key nutrient for microbial growth—from the water, the researchers essentially starved the microorganisms, limiting their ability to proliferate.
The team used regular dosing with silver fluoride, a potent antimicrobial agent that kills planktonic (free-floating) microorganisms before they can attach to surfaces and form biofilms.
What made this research particularly innovative was its use of a defined multidomain consortium of organisms—specifically, three bacteria and one fungus that had been frequently isolated from the ISS water system. This approach accurately simulated the actual microbial challenge faced in space missions 3 .
The Montana State University research team designed a comprehensive experiment to test these strategies both individually and in combination, using CDC Biofilm Reactors equipped with different materials commonly found in water systems 3 .
| Material/Reagent | Function in Experiment |
|---|---|
| Sher-Loxane® 800 coating | Creates anti-fouling surface that prevents microbial attachment |
| Silver fluoride biocide | Kills planktonic microorganisms before biofilm formation |
| Phosphorus-free medium | Limits microbial growth by removing essential nutrients |
| Synthetic ISS wastewater medium | Accurately simulates actual conditions in spacecraft water systems |
| CDC Biofilm Reactors | Standardized equipment for growing and studying biofilms |
| PTFE and Inconel disc coupons | Representative materials from water system components |
| Defined microbial consortium | Mixed culture of ISS-isolated bacteria and fungi for realistic testing |
Researchers applied the Sher-Loxane® 800 coating to test surfaces, including PTFE and Inconel materials commonly used in water system components.
The team introduced a carefully designed consortium of microorganisms—including three bacterial species and one fungal species frequently isolated from ISS water systems—into the experimental setup.
The researchers tested seven different combinations of the three control strategies, plus a control group with no interventions, to evaluate both individual and combined effectiveness.
Over seven days, the team measured biofilm accumulation using sophisticated monitoring techniques, including microscopy and viability assays, to quantify how well each approach worked.
This comprehensive experimental design allowed the researchers to not only test individual strategies but also discover how these approaches might work together synergistically 1 3 .
The findings from this seven-day experiment revealed both expected and surprising insights into biofilm control, with the combination of all three methods demonstrating remarkable effectiveness.
| Strategy | Effectiveness | Key Findings |
|---|---|---|
| Coating Only | Moderate | Key factor in reducing initial attachment |
| Nutrient Removal Only | Limited | Partial reduction in biofilm accumulation |
| Biocide Only | Moderate | Effective against planktonic microbes |
| Coating + Nutrient | Good | Better than individual approaches |
| Coating + Biocide | Very Good | Strong reduction in viable biofilm |
| All Three Combined | Excellent | Near-elimination of viable biofilm |
The results demonstrated that while each individual strategy provided some benefit, the real power emerged when these approaches were combined. The presence of the coating proved to be a key factor in reducing biofilm accumulation across all test scenarios. However, the most striking outcome came from combining all three methods: together, they reduced viable biofilm to just above the detection limit after seven days of growth 1 2 .
This synergistic effect suggests that the different strategies work through complementary mechanisms:
When combined, these approaches create a hostile environment for biofilms at multiple stages of their development, from initial attachment to mature community formation.
As we look toward long-duration missions to the Moon and Mars, where resupply becomes impossible and systems may experience extended dormancy periods, biofilm control becomes even more critical. The research community is responding with innovative new technologies that build upon the multimodal approach.
| Technology | Mechanism | Potential Application |
|---|---|---|
| Passivated Silver Nanoparticles | Controlled release of antimicrobial silver ions | Long-lasting protection during mission dormancy |
| UV-C Side-Emitting Optic Fibers | DNA damage to microorganisms using ultraviolet light | Chemical-free disinfection in water systems |
| Sulfide-Passivated Silver Coatings | Extended antimicrobial activity through controlled ion release | Complex metallic surfaces like bellows |
| Surface-Adapted Hyperbranched Polymers | Prevention of microbial attachment through material science | Advanced anti-fouling coatings |
One particularly promising innovation comes from researchers developing passivated silver nanoparticles. By treating silver nanoparticles with sulfide, scientists can control the release rate of antimicrobial silver ions, potentially extending the active life of the coating for many months—a crucial feature for long-duration missions 5 .
Meanwhile, Arizona State University's Germicidal Ultraviolet Light Biofilm Inhibition (GULBI) experiment, which launched to the ISS in September 2025, is testing UV-C light delivered through thin, flexible, side-emitting optical fibers as a potential chemical-free alternative for biofilm control 8 .
As Westerhoff's team observes how germicidal ultraviolet light breaks bacterial DNA and prevents repairs in microgravity, their research could lead to solutions that reduce the need for chemical disinfectants—especially valuable given the exorbitant cost of sending supplies to space (estimated at $20,000 for a 500ml bottle of disinfectant) 8 .
While this research directly addresses challenges in space exploration, its implications extend far beyond spacecraft water systems. On Earth, biofilms cause an estimated $4 trillion in damage annually through corrosion, mold growth, harboring pathogens in medical devices, and increased energy consumption in industrial systems 8 .
The multimodal approach pioneered for space applications could revolutionize how we manage biofilms in:
As McLean notes, "By studying how biofilms behave in extreme environments like microgravity, we can improve both our fundamental understanding and our ability to prevent their widespread problems here on Earth" 8 .
The battle against biofilms in spacecraft water systems highlights a broader truth about space exploration: the challenges of sustaining human life in extreme environments drive innovation that benefits both spacefaring and Earth-bound humanity. The multimodal approach—combining coatings, nutrient management, and biocides—represents a sophisticated understanding that complex problems rarely have simple solutions.
As we prepare for longer missions further into space, this research provides crucial insights into creating sustainable, resilient life support systems that can operate reliably for years without maintenance. The solutions being developed today will not only protect astronauts on their journey to Mars but may also lead to cleaner, more efficient water systems here on Earth.
In the end, controlling the "slimy goo" that threatens to clog our path to the stars exemplifies the ingenuity and persistence required to become a spacefaring civilization—one that can sustainably live and thrive far beyond our planetary cradle.