The International Space Station (ISS) is one of the most unique places where life has existed, outside of low Earth orbit. And research today is finding that bacteriophages—bacteria that eat bacteria—can behave strangely in space.
Scientists have learned how phages interact with them Escherichia coli bacteria aboard the ISS and compare them to pears grown on Earth. Phages that live in space take longer to infect their hosts, while both bacteria and viruses make unusual changes in response to each other and the microgravity conditions of the ISS, they found. The findings also suggest that phages in space could develop useful genetic mutations for humans at home.
“Microbes continue to evolve under microgravity, and they do so in ways that are not always predictable in Earth-based experiments,” senior study author Vatsan Raman, a biomolecular and cellular engineer at the University of Wisconsin-Madison, told Gizmodo.
Phases in space
Studies have shown that many bacteria and other microorganisms can thrive on the ISS, including microorganisms left behind by astronauts’ visits. But according to Raman, there has been little research examining how these space viruses interact, particularly with phages and the bacteria they infect to make more of them.
“Most experiments on microbial evolution assume constants like Earth-like physical conditions, but spaceflight changes important aspects of the environment—how fluids mix, how cells assemble, and how physical forces shape cellular physiology,” he explained. “Phage infection is highly dependent on transport, assembly rates, and host physiology, all of which can clearly change in space. We wanted to test whether microgravity simply slows down these processes, or whether it pushes phages and bacteria into completely different evolutionary paths.”
They were focusing on a particular type of phage that likes to feast on it E. coliknown as T7.
The ISS phages were slow to infect their prey at first, perhaps because fluids don’t mix as well under microgravity conditions, according to Raman. But once infection has occurred, both phages and bacteria change rapidly and are often very different from their Earth counterparts. Bacteria have evolved mechanisms that seem to enhance their defenses against phage infection and improve their survival in space, while phages have evolved to be more easily infected. E. coli. In addition, some of the genetic changes observed in the spacecraft were unlike anything seen on Earth.
“The key takeaway is that microgravity doesn’t just slow phage infection—it reshapes the way phages and bacteria co-evolve,” Raman said. “We’ve seen unexpected mutations, including those that don’t show up well in standard laboratory settings.”
The team’s findings were published Tuesday in PLOS Biology.
What does this mean
The findings clearly have implications for space travel, especially long-duration missions. The microbes that inhabit the ISS and other space stations in the future are not just static visitors, and it is quite possible that they could evolve in ways that have a real impact on the health of astronauts and the environment in general, Raman said.
That scary possibility aside, phages in space could also help humanity. The team’s experiments on Earth found that several mutations observed on the ISS made the phages better at attacking T7-resistant strains. E. coli causing urinary tract infections in humans.
Patches are already being developed as an alternative treatment for drug-resistant infections. And while it wouldn’t be possible to do these kinds of experiments regularly on the ISS, learning exactly how microgravity can shape the evolution of these microbes could allow scientists like Raman to apply those lessons to studies on Earth.
“I hope that this work encourages researchers to think about space not as a place to reproduce Earth’s experiments, but as a completely different place that may reveal life sciences—ideas that ultimately circle back to improve research and applications here on Earth,” he said.
Looking ahead, the researchers now hope to better understand the specific genes and mutations of the T7 phases that appeared under microgravity, especially those that are not easily created in a standard lab. They also hope that similar studies in the future will reveal how environment can change the biology of complex bacterial communities or medically relevant pathogens.
