Spaceflight enhances the ability of viruses to infect bacteria

Viruses develop tricks to attack bacteria without the help of gravity

By KR Callaway edited by Sarah Lewin Frasier

Bacteria and the viruses that infect them are perpetually at war. Their deadly clashes push both types of microbes to evolve new traits that meet the challenges of every environment they inhabit, from the human digestive tract to seafloor hydrothermal vents. even in the harsh conditions of space.

To see how microgravity changes certain microbes, researchers sent bacteria-infecting viruses called bacteriophages to the International Space Station, and they found that the viruses adapted in ways that made them even more effective against infection.

In the experiment, detailed In Biology PLOSthe team incubated specimens of the common laboratory bacteriophage T7 alongside its enemy, Escherichia coli bacteria, for varying durations. They conducted the same experiment on Earth and in space; Viruses raised on Earth infected bacteria within two to four hours, but those in space took more than four hours to break down the bacteria’s defenses. The infection took longer to orbit because microgravity is an unknown stressor to which both microbes must adapt, the researchers suggest.

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Once viruses adapted to microgravity by subtly changing shape, they became even more effective bacteria killers. “A simple microgravity experiment reveals these mutations that have much higher effectiveness against pathogens,” says lead study author Srivatsan Raman, a chemical and biological engineer at the University of Wisconsin-Madison.

The difference between Earth and space may have to do with mixing. “Under normal gravity, the movement of fluids continually stirs the environment, increasing the chances of viruses and bacteria meeting,” explains Ester Lázaro, an astrobiologist who was not involved in the study. “In microgravity, this natural mixing is considerably diminished, or even disappears completely.” To overcome this lack of mixing, microbes grown in low gravity changed at the genetic level. Bacteriophages have acquired mutations that slightly change the shape and structure of their outer membranes, helping them, for example, to latch on to the bacteria they attack.

Upon their return to Earth, the space viruses were placed alongside another strain of E.coli responsible for particularly stubborn urinary infections and frequently resistant to bacteriophages. Evolved viruses were able to kill this bacteria, which Raman says is “really very promising.” If exposing these bacteria-targeted viruses to new environmental stressors makes them more potent, scientists might be able to create versions strong enough to help the body fight off treatment-resistant bacteria.

“T7 is one of our iconic model organisms, so we know a lot about this bacteriophage,” explains Evelien Adriaenssens, a researcher at the Quadram Institute in England, who was not involved in the study. “It was cool to see that if you go to a different environment, new knowledge arises.”