Scientists studying life in space have made a remarkable discovery aboard the International Space Station (ISS) that could reshape our understanding of microbial interactions and even point to new ways of tackling antibiotic-resistant infections back on Earth. The study, published in the peer-reviewed journal PLOS Biology, reveals that microgravity — the near weightless conditions experienced in low Earth orbit — fundamentally changes how bacteriophages (viruses that infect bacteria) and their bacterial hosts evolve and interact.
In the experiments, researchers from the University of Wisconsin-Madison sent samples containing Escherichia coli (E. coli) bacteria and a type of bacteriophage called T7 to the ISS and compared how the microbes behaved in space versus identical samples kept on Earth. These tiny organisms, long studied on our planet for their evolutionary “arms race” — where bacteria evolve defenses and viruses evolve ways around those defenses — provided a unique window into how life adapts in space.
What the scientists found was striking. In microgravity, the initial infection process between bacteriophages and bacteria was delayed compared to Earth. The reduced effects of gravity meant the physical environment for viral infection — such as fluid movement and how often viruses and bacteria bump into one another — was very different. Still, over longer periods, the T7 phage did successfully infect its bacterial host aboard the ISS, but the evolutionary path it took was distinct from its Earth-bound counterparts.
Whole-genome sequencing of the returned samples revealed that both the phages and the bacteria accumulated unique mutations as they adapted to microgravity. The phages tended to develop mutations that could increase their ability to bind to bacterial cell receptors and enhance infection efficiency, while the E. coli populations evolved genetic changes that appeared to increase their resistance to viral attack and help them cope with the stresses of a near-weightless environment.
To dig even deeper into the mechanisms at play, the research team used a technique called deep mutational scanning to analyze changes in the virus’s receptor-binding proteins — the molecular “keys” that let the phage latch onto bacterial cells. This analysis showed that the spectrum and location of mutations selected for in microgravity differed substantially from those favored on Earth. These differences reflect how the physical environment of space can shape biological evolution in ways scientists are only beginning to understand.
Perhaps most intriguingly, when researchers took some of the phage variants that evolved aboard the ISS and tested them back on Earth, they found that some of these space-adapted viruses were better at infecting drug-resistant strains of E. coli than their Earth-incubated counterparts. This unexpected result suggests that studying microbial evolution in microgravity could offer valuable insights into engineering bacteriophages as tools against tough bacterial infections — a major challenge in human medicine.
“Space fundamentally changes how phages and bacteria interact: infection is slowed, and both organisms evolve along a different trajectory than they do on Earth,” the researchers explained in the PLOS Biology publication. These findings hint that the ISS could serve not just as a platform for understanding how life adapts off our planet, but also as a living laboratory for discovering solutions to terrestrial problems like antibiotic resistance.
The implications of this research are wide-ranging. For space missions planned decades into the future, understanding how microbes behave in orbit is critical for astronaut health and closed-environment life support systems. But perhaps more immediately, the distinct evolutionary pathways observed in microgravity could inspire new strategies in biotechnology and phage therapy — the emerging medical approach that uses viruses to target and kill antibiotic-resistant bacteria.
As scientists continue to explore life at the edge of space, it’s clear that the microgravity environment aboard the ISS is teaching us not just about how life survives beyond Earth, but also offering fresh insights into the basic rules governing life and disease back home.
