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Studying Microbes in Space

Powering Innovation

In spaceflight, even the tiniest things can mean the difference between groundbreaking success and catastrophic failure.

Two Texas State University researchers are investigating microscopic organisms in the microgravity environment of space.

Man conducting experiment on ISS

Dr. Robert McLean is a Regents’ Professor of biology, working with Starla Thornhill, a doctoral student in Texas State’s aquatic resources and integrative biology program. Along with colleagues at Arizona State University, the University of Colorado, and NASA Johnson Space Center, they are sending bacterial experiments to the International Space Station (ISS). Their goal is to learn how microbes behave in space for the purpose of improving future long-term human space missions. Along the way, they’ll gain a better understanding of microbial behavior in general for applying to earth-bound situations.

McLean and Thornhill are focusing on a form of growth called biofilms. Biofilms are accumulations of microbes that attach to a surface, like dental plaque on teeth or slime on a river rock. These films also grow inside plumbing or filtration systems, and on the surfaces of medical devices such as catheters and artificial joints. “Biofilms are really a multibillion dollar problem worldwide,” says McLean. And that problem isn’t limited to earth. The water filtration system on the ISS is vital to astronauts’ health and survival, since it recycles and purifies their only water supply. Part of the purification process involves trying to control bacteria; a biofilm clog in a filter could lead to the risk of infection.

"It costs so much money to send something to space that if your experiment fails, you generally don’t get the opportunity to redo it."

McLean and colleagues were the first researchers, in 2001, to publish evidence that biofilms could form in microgravity at all. Now, McLean and Thornhill are particularly interested in polymicrobial biofilms: communities made up of more than one type of organism. McLean notes that most of the relatively few space-based bacterial research projects have involved pure cultures, consisting of a single species. But that’s not how microbes usually grow in nature — more often, multiple types coexist in close proximity. “Usually if you mix bacteria, they compete,” McLean says. “One becomes dominant.” The group’s experiments will show how these multi-species dynamics play out in microgravity. This is especially important because previous research has shown that microorganisms act surprisingly in space: some become more virulent than they are on earth, others less so.

Microbes are microscopic organisms, including bacteria, viruses, and fungi.


Objects in the International Space Station experience microgravity, a force one millionth as strong as that felt on earth.

EcPa Biofilm

The team’s experiments will be composed of two common infection-causing bacteria: Pseudomonas aeruginosa and Escherichia coli. In order to see and then analyze the different “neighborhoods” within these polymicrobial biofilms, Thornhill has prepared a strain of E. coli containing a marker that glows red under certain light; the strain of P. aeruginosa has a similar marker that glows green. This will allow the researchers to count the number of bacterial cells present in the biofilm and to track their distribution.

Thornhill has been managing the long, detailed process of designing experiments that will succeed within the unique constraints of a NASA mission. “A space flight experiment is a one-shot deal,” she explains.

"It costs so much money to send something to space that if your experiment fails, you generally don’t get the opportunity to redo it. We have to account for unexpected flight delays, and ensure that our experiment is stable if the scheduled launch is delayed or cancelled. A major thing we have to take into account is crew safety. We have to ensure that our bacteria and chemicals will remain contained so that resident crew is not exposed."

The experiments are scheduled to launch to the ISS aboard a SpaceX ship in late 2019. At the same time as the bacteria float in space, the researchers will duplicate the experiments as best they can on earth for comparison. They’ll use a modeled microgravity environment created by rotating a petri dish vertically, very precisely, so that the microbes experience an effect similar to that of orbit. A horizontally rotating dish, subject to gravity’s normal pull, will act as a control.

In the end, the researchers hope to better understand the risks associated with these microbial biofilms in space, risks both of infection in humans and of corrosion to the stainless-steel piping of the ISS. If astronauts are to spend more time in space — such as on a moon base or a mission to distant Mars — having the safest microbe-resistant water systems will be more important than ever. And the experimental results may lead to earth-based biomedical applications as well. 

“It gives insight into how organisms can live in environments we haven’t thought of,” McLean says. “A discovery that was made here might help us get to Mars.”

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