Viruses that infect bacteria can operate in near zero gravity aboard the International Space Station (ISS).

However, the pace of infection will change and both viruses and bacteria will begin to evolve along different paths than on Earth.

Team led by Phil Huss University of Wisconsin-Madison I tracked what happened when bacteriophage T7, a classic virus used in the lab, encountered its normal host, E. coli, in a microgravity environment.

The experts compared corresponding samples grown in orbit and on Earth to see how the infection unfolded and what genetic changes accumulated over time.

mutated phages in space

On Earth, a phage “wins” by hitting a suitable bacterium, attaching to it, injecting its genetic material, and forcing the cell to manufacture a new bacterium. virus particle.

The timing of that encounter depends not only on biology but also on physics. Mixing, convection, sedimentation, and constant exchange of nutrients and waste products all increase the likelihood that viruses and bacteria will collide.

In microgravity, that background motion changes. The fluid no longer circulates in the same way because there is almost no convection due to buoyancy.

Microorganisms experience very different environments with respect to transport, diffusion, and local accumulation of byproducts.

At the same time, bacteria can change their physiology. space flight Conditions – including the type of outer membrane molecule that the phage uses as a “handle” to attach.

Therefore, the big question is not just “Can infection occur?” It’s whether the whole coevolutionary tug of war between bacteria and phages plays out differently if the physical world is weird.

A simple test on the ISS

To isolate the effects of microgravity as accurately as possible, the researchers prepared two identical sets of samples sealed in cryovial tubes. One set went to the ISS. The other remained on Earth as a control.

The research team used a non-motile E. coli strain (BL21) to remove swimming mixing from the equation and incubated everything at 37°C without shaking.

The experts then looked at what happened at short time points (1, 2, and 4 hours) and long time points (23 days).

The short window was aimed at catching early infection dynamics. The long time frame gave both organisms time to reproduce and adapt, if possible.

Space phages behave differently

Under typical laboratory conditions, T7 can be infected with E. coli and rapidly rupture. The experiment also showed a significant slowdown in terrestrial samples, with infection effectively occurring in 2 to 4 hours.

In microgravity, the deceleration was even stronger. For the first few hours, the phages showed no clear signs of replication as well.

But importantly, it wasn’t a dead end. By the 23rd mark, the phages that have grown in space have clearly succeeded in replicating and surviving, meaning that productive infection is still occurring only on a dramatically extended timeline.

Timing is critical to survival, so a “slow start” is key. The delay changes the number of bacterial cells available, how stressed the bacterial cells are, and what kinds of defenses can be put in place before the virus fully develops.

Various evolutionary solutions

After the team confirmed the long-term infection results, they looked at the genetics.

Whole genome sequencing They showed that both viruses and bacteria are accumulating new mutations, but the patterns are different in space and on Earth.

On the phage side, mutations spread throughout the genome, including in proteins related to infectivity and host interactions.

In microgravity, certain phage genes stand out in enhanced changes, suggesting that the virus is being propelled toward a different set of “best moves” than the one it normally uses on Earth.

bacteria under pressure

On the bacterial side, mutations were particularly common in genes related to the outer membrane and stress responses.

These are exactly the kinds of systems that can help bacteria cope with microgravity and make it harder for phages to get caught.

Sequencing also suggested that phage pressure itself was a major factor. Bacteria exposed to phages accumulated more pronounced mutations than bacteria cultured without phages.

In other words, the “arms race” did not stop even in space. I just took a different route.

The key to solving the infection

The team then focused on one key tool: the T7 receptor-binding protein. The T7 receptor-binding protein is a part of a phage that recognizes the bacterial surface and helps initiate irreversible binding.

They used a deep mutational scan to essentially generate a large library of single amino acid variants in key regions of the protein, mapping which changes helped or hurt the phage under each condition.

The result was no small adjustment. The mutant “fitness landscape” looked very different in microgravity compared to Earth.

This result indicates that the host environment has changed enough to change the reward the phage receives with each mutation.

space phage on earth

Here’s a twist that makes the story bigger than astrobiology. The researchers used microgravity-based insights to assemble combinatorial phage mutants.

The variants were tested against two clinically isolated uropathogenic E. coli strains (UTI1 and UTI2) associated with urinary tract infections.

These are strains that are resistant to wild-type T7 under normal land conditions. The microgravity-informed mutants showed enhanced activity, whereas the equivalent “Earth-informed” library did not show a similar increase in activity.

That doesn’t mean the universe is a magical phage factory. But it suggests microgravity It can reveal evolutionary pathways and useful molecular tweaks that are difficult to discover under standard laboratory conditions.

Discoveries in extreme environments

On long-duration spaceflights, the immediate lessons learned are practical. microbial ecosystem In orbit, it may behave in ways that are familiar in general (infections still occur) but unfamiliar in details (timing, selection pressures, adaptive pathways).

In the case of global medicine, the lesson is more opportunistic. Extreme environments act like discovery engines, revealing new design principles for engineering phages that perform better against hard-to-treat bacteria.

“Space fundamentally changes how phages and bacteria interact. Infection is slower and both organisms evolve along different trajectories than on Earth,” the researchers noted.

“By studying these space-driven adaptations, we have identified new biological insights that will allow us to engineer phages with far greater activity against drug-resistant pathogens on Earth.”

The research will be published in a journal PLOS Biology.

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