Scientists Reveal How Microgravity Forces Viruses to Evolve Into More Efficient Killers

Life beyond our atmosphere presents unique challenges that we are only beginning to understand. Recent findings suggest that the environment aboard the International Space Station may be altering how pathogens develop and behave. These biological shifts could pose significant new threats to astronauts' well-being during long-term missions.

Microbes and their viral predators, or phages, remain trapped in a constant cycle of mutual adaptation. Phages and the bacteria they target exist in a state of perpetual biological conflict. Research from the International Space Station (ISS) indicates, however, that this competitive development shifts onto a new path when encounters occur in microgravity.

In this ongoing struggle, bacteria build stronger defences to survive, while phages find clever ways to break through. New research featured in the 13 January issue of PLOS Biology explores how this fight plays out in orbit, providing knowledge that may lead to superior treatments for hard-to-treat infections on our own planet.

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Testing the Speed of Infection

The team monitored groups of E. coli under attack by the T7 virus across two different settings. While one group of microbes developed in orbit, a secondary set of twins grew under normal conditions on the ground. Results from the orbital data indicated that the low-gravity environment transformed both the pace and the basic characteristics of the viral onslaught.

Even though the phages remained lethal to their hosts in the stars, the timeline for destruction stretched out compared to the samples on the ground. This matched earlier predictions from the team, who believed that the way liquids behave without weight prevents the microbes from bumping into each other as frequently.

'This new study validates our hypothesis and expectation,' explained Srivatsan Raman, an associate biochemistry professor at the University of Wisconsin-Madison. Here on the ground, the environments where viruses and bacteria live are in constant flux, driven by gravity as heat creates currents and dense materials fall. These forces keep the inhabitants in a regular state of contact.

Without gravity to churn the environment, everything in orbit remains suspended and still. Since these encounters became far less frequent, the viruses were forced to adjust to a more patient existence, refining their ability to latch onto any host that drifted nearby.

Cracking the Genetic Code

Researchers believe that deciphering this unusual evolutionary path may help develop novel phage-based treatments. These modern medical approaches use viruses to either eliminate harmful germs directly or weaken them so that standard antibiotics can finish the job.

'If we can work out what phages are doing on the genetic level in order to adapt to the microgravity environment, we can apply that knowledge to experiments with resistant bacteria,' explained Nicol Caplin, an ex-astrobiologist with the European Space Agency not connected to the research, via email. 'And this can be a positive step in the race to optimise antibiotics on Earth.'

Detailed DNA mapping showed that both microbes and viruses aboard the ISS developed unique genetic changes absent in the ground samples. The orbital phages acquired traits that increased their infectiousness and enabled them to latch onto bacterial docking sites more effectively. At the same time, the E. coli evolved ways to fend off these strikes—such as altering their surface structures—while also becoming better suited for life in low gravity.

From Cosmic Research to Clinical Use

Following this, scientists utilised a method known as deep mutational scanning to examine mutations in viral proteins that bind to the host. They discovered that the adjustments forced by the unusual conditions in space might have real-world benefits here on Earth.

After being returned to Earth, the phages' newly evolved proteins proved much more effective at attacking E. coli variants that frequently cause urinary tract infections. These specific germs are usually immune to the standard T7 virus, yet the space-modified versions could overcome them.

The Future of Astronaut Health

'This discovery was a stroke of luck,' Raman remarked. 'The idea that the mutated viruses we found on the ISS could actually destroy disease-causing germs here on the ground was something we never anticipated.'

'These results show how space can help us improve the activity of phage therapies,' said Charlie Mo, an assistant professor in the Department of Bacteriology at the University of Wisconsin-Madison who did not participate in the research. 'However,' Mo added, 'we do have to factor in the cost of sending phages into space or simulating microgravity on Earth to achieve these results.'

Beyond treating patients on the ground, Mo indicated that this work may lead to more potent viral treatments for use in low gravity. 'This could be important for astronauts' health on long-term space missions — for example, missions to the moon or Mars, or prolonged ISS stays.'