Zero gravity had unexpected effects on E. coli samples, causing them to behave differently. That could present problems trying to treat them.

When astronauts head into space, they don’t go alone.

Billions of bacteria are also along for the ride.

Now, scientists have discovered that these microorganisms behave quite differently in zero gravity.

A recent study, published in Frontiers in Microbiology, found that E. coli bacteria grows differently in space compared to how it grows on Earth.

Changes to this bacterium, which occurs naturally in the gastrointestinal tract of humans, could make it more difficult to treat with common antibiotics in space.

Researchers from the University of Colorado Boulder, along with scientists at the University of Copenhagen, German Aerospace Center, and The Pontifical Catholic University of Rio Grande do Sul in Brazil, participated in the research.

They studied changes to Escherichia coli that was grown aboard the International Space Station compared to E.coli bacteria grown on Earth.

Luis Zea, PhD, lead study author, and a research associate at the BioServe Space Technologies in the University of Colorado Boulder, said they wanted to figure out how bacteria physically changed in space.

“We knew bacteria behave differently in space and that it takes higher concentrations of antibiotics to kill them,” Zea said in a statement. “What’s new is that we conducted a systematic analysis of the changing physical appearance of the bacteria during the experiments.”

They found that the bacteria had less volume overall, but there was significant increase in cell count and change in how the bacteria grew.

Overall, the team discovered there was a 13-fold increase in total cell count for the E.coli grown in space compared to the bacteria grown on Earth.

The cells in space were also just 27 percent of the volume of their Earth-bound counterparts.

Additionally, the envelope thickness of the cell increased between 25 to 43 percent, according to the study findings.

The bacteria also started to grow in clusters rather than growing more evenly dispersed as on Earth.

Dr. William Schaffner, an infectious disease expert at Vanderbilt University School of Medicine in Tennessee, said that all of these physical changes to the bacteria could make them more impervious to the effects of antibiotics.

“The fact that you get kind of smaller bacteria that are actually thicker bacteria, and they grow in clumps,” he told Healthline. “All three of those things might well make it more difficult for certain antibiotics to affect the bacteria. There is no doubt.”

Schaffner explained that if the cell surface is thicker, it could make it “more difficult for antibiotics to penetrate bacteria and do their dirty work.”

He also pointed out that when bacteria grow in clumps, the antibiotic has to attack the outer layer of cells before reaching the center, likely requiring more antibiotics to fully kill the bacteria.

Schaffner said it’s important to understand how bacteria like E.coli will change in space, since the bacteria live naturally on or in the human body and are the most common cause of bladder and kidney infections.

“No matter how thoroughly the astronauts shower, they will be taking billions of bacteria with them into space,” he said.

This information could be key as astronauts spend more and more time in orbit.

NASA is currently planning on sending astronauts to an asteroid by 2025 and to Mars sometime in the 2030s.

Already, astronauts are spending more time on the International Space Station so that scientists can understand how the human body is affected by living miles above the Earth.

“Engineers and scientists around the country are working hard to develop the technologies astronauts will use to one day live and work on Mars, and safely return home from the next giant leap for humanity,” NASA officials said of their plans for the future.