A delayed infection aboard the International Space Station led to a surprising discovery: spaceflight conditions force viruses and bacteria into an entirely different evolutionary battle than anything seen on Earth.
Inside sealed cryovials orbiting more than 400 kilometers above Earth, bacteriophages and E. coli behaved in unexpected ways that reshaped their genetics and their interactions.
The Research Team and Journal
The work was led by scientists from the University of Wisconsin–Madison in collaboration with Rhodium Scientific Inc., a company specializing in spaceflight-enabled biotechnology research. The experiment was carried out aboard the International Space Station (ISS), where microgravity provided a unique environment to study virus–bacteria interactions that cannot be replicated on Earth.
The findings were published in PLOS Biology on January 13, 2026, offering one of the most detailed analyses to date of how spaceflight reshapes microbial evolution and infection dynamics.
The Problem Before This Study
On Earth, phages find and infect bacteria quickly thanks to natural fluid mixing, sedimentation, and convection. In space:
- Liquids do not mix naturally
- Bacteria experience stress responses not seen on Earth
- Diffusion slows molecular movement
- Outer membrane structures that act as phage receptors may change
Researchers did not know whether phages could reliably infect their hosts in orbit or how microgravity might alter microbial evolution over time.
“Our study offers a preliminary look at how microgravity influences phage host interactions.”
Lead research team, University of Wisconsin–Madison
How the Experiment Worked
Inside the ISS, researchers incubated:
- Wild type T7 bacteriophage
- Non motile E. coli BL21
- A library of 1,660 engineered phage receptor binding protein variants
The microbes were frozen, launched to space, thawed, incubated for 1, 2, 4 hours, or 23 days, then refrozen and returned to Earth for sequencing and viability tests. Parallel Earth controls matched ISS incubation times.
The key question: Does microgravity change how viruses infect and evolve with bacteria?
What Is New in This Study
The ISS environment produced completely different evolutionary pressures for both organisms, leading to the following observations.
A major delay in phage infection
On Earth, T7 infects E. coli in 20 to 30 minutes. In orbit, no infection occurred for the first 4 hours, yet by day 23, phages had fully replicated.
Unique high fitness mutations in both phage and bacteria
- Phage structural genes gp7.3, gp11, and gp12 accumulated numerous adaptive changes in microgravity.
- Bacteria evolved mutations in outer membrane proteins, stress response regulators, and lipopolysaccharide synthesis genes, reshaping susceptibility to phages.
A new mutation (V26I) swept through the entire phage population only in microgravity, suggesting a strong advantage under spaceflight conditions.
Deep mutational scanning revealed selection patterns that do not exist on Earth
Mutations that performed well in space were often poor performers on Earth, showing completely different survival rules.
“Space fundamentally changes how phages and bacteria interact. Infection is slowed and both organisms evolve along a different trajectory than they do on Earth.”
Study authors
Measured Results and Evidence
Phage Activity
- Earth: 5 to 7 log increase in phage titer within 4 hours and bacteria dropped 4 to 5 logs.
- ISS: No phage increase for 4 hours and a 4 log increase only after 23 days.
Bacterial Survival
- Bacteria without phages crashed by 6 to 7 logs early in microgravity, suggesting physiological stress that may have been worsened by freeze thaw.
Genetic Adaptation
Dozens of de novo mutations emerged.
- Phage mutations concentrated in structural components of the infection machinery.
- Bacterial mutations appeared in genes controlling outer membrane shape, LPS pathways, and stress responses.
These patterns strongly confirmed coevolution rather than random drift.
“Exploring phage activity in non terrestrial environments reveals novel genetic determinants of fitness and opens new avenues for engineering phages for terrestrial use.”
Research team statement
Why This Matters Now
Understanding microbial evolution in microgravity is critical because:
- Long duration missions such as Moon and Mars expeditions depend on stable microbial ecosystems
- Spacecraft, life support systems, and astronaut health can all be influenced by shifts in microbe virus interactions
- Phage therapy is becoming a major tool against antibiotic resistant infections
- Space driven mutation patterns can help design more potent therapeutic phages
This study shows that space is a powerful evolutionary environment capable of producing phage variants with real world medical potential.
“By studying those space driven adaptations, we identified new biological insights that allowed us to engineer phages with far superior activity against drug resistant pathogens back on Earth.”
Lead scientist
The authors note that microgravity exposed previously unrecognized functional regions of the phage receptor binding protein, enabling rapid identification of beneficial mutation combinations that Earth experiments had missed.
“The success of this approach helps lay the groundwork for future phage research aboard the ISS.”
Study authors
Put simply: space helped reveal evolutionary solutions invisible on Earth.
Real World Applications
Health and Medicine
The microgravity selected phage mutations produced variants that:
- Infected previously resistant uropathogenic E. coli
- Formed larger and more potent plaques
- Outperformed all Earth selected variants on clinical isolates
This suggests that space conditions could help design next generation phage therapies.
“Microgravity revealed evolutionary solutions we simply cannot observe on Earth.”
Research team commentary
Spaceflight Microbiology
- Protect astronauts from opportunistic infections
- Improve closed loop bioreactors
- Design safer microbial systems in spacecraft environments
Biotechnology
- Explore protein sequence space
- Reveal hidden functional constraints
- Evolve specialized biomolecules
What Comes Next
The authors highlight several next steps:
- Test intermediate time points to pinpoint when infection begins
- Use motile bacterial strains
- Perform onboard sequencing to avoid freeze thaw effects
- Study additional phages and microbial communities
- Explore intentional phage engineering in microgravity for medical use
These directions will help refine scientific understanding of microbial adaptation in orbital environments.
“We are only beginning to understand how space alters microbial evolution. More studies are needed to explore this environment’s full potential.”
Research team spokesperson
Conclusion
This study shows that:
- Microgravity slows but does not stop phage infection
- Spaceflight conditions reshape how bacteria and viruses evolve together
- These space driven mutations can produce improved phage therapy candidates
Space is not only a challenge for life. It is an evolutionary laboratory that reveals biological strategies we cannot discover on Earth.
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