NASA selects Texas State team to study bacterial growth impact on ISS

Posted by Jayme Blaschke
Office of Media Relations
September 6, 2016

NASA’s Physical Sciences Research Program has awarded Robert McLean, a professor in the Department of Biology at Texas State University and Texas State University System Regents' Professor, a grant to study biofilms in microgravity.

McLean’s project, "Polymicrobial Biofilm Growth and Control during Spaceflight," is one of 16 flight proposals accepted by NASA for research to be conducted aboard the International Space Station (ISS) as part of the MaterialsLab program. The experiments in the various disciplines of physical science will reveal how physical systems respond to the near absence of gravity. They will also reveal how other forces that on Earth are small, as compared to gravity, can dominate system behavior in space.

The behavior of microorganisms in microgravity is poorly understood, McLean explained, and an experiment of his flown on the space shuttle in 1998 provided the first evidence that biofilms could even form in microgravity conditions. Aboard the ISS, bacterial colonies form biofilms in filtration systems that are resistant to disinfectants. Common examples of biofilm on Earth include plaque that forms on teeth and slime that grows on river rocks. Unchecked, these biofilms can lead to clogs and, potentially, corrosion in critical systems.

McLean is assisted in his research at Texas State by Starla Thornhill, an aquatic resources doctoral student. Using a liquid-filled bioreactor, which bears passing resemblance to a vertically-rotating petri dish, McLean and Thornhill grow colonies of E. coli and Pseudomonas aeruginosa bacteria in the laboratory under the simulated weightless conditions of space.

“We’re going to put genes for two different florescent proteins in these organisms. If things work as planned, the E. coli will look red under a microscope and the Pseudomonas will look green,” McLean said. “When you’re looking at them, you can just simply tell the two organisms apart and see how they’re attached, whether they’re huddled up with each other or dispersed, whether you have a Pseudomonas neighborhood or an E. coli neighborhood. And does this association vary going from a full gravity to microgravity? We don’t know.”  

A growing body of evidence indicates mixed-culture biofilms behave quite differently from those formed by a single culture, so the Texas State researchers will study the traits of E. coli and P. aeruginosa growing together and their effect on a stainless steel substrate—one of the primary materials used in ISS environmental systems. Once comprehensive baseline data is assembled from the laboratory work, the project will advance to direct research aboard the ISS itself.

“We can look at it with a microscope that’s on board the space station, but we also have another microscope that will be looking at it the same time on Earth. So we will be doing a simultaneous examination and be in contact with the crew on the space station for that,” McLean said. “This will likely happen toward the end of the second year or beginning of the third year of the grant. It’s a four-year grant, and the fourth year will be post-flight analysis.”

The results of the research will be of significant interest to ISS mission planners, as well as those of long-duration space flight, including possible future missions to Mars. The research also has the potential for applications in biotechnology fields.

Other members of McLean’s research team include co-investigators Cheryl Nickerson, Jennifer Barrila and Jiseon Yang of Arizona State University; and Mark Ott of NASA’s Johnson Space Center (JSC), along with collaborators Simon Clemett of the JSC and Mayra Nelman-Gonzalez of Wylie Laboratories. 

The MaterialsLab program provides a platform to accelerate materials development and make new discoveries using data from the investigations performed aboard the orbiting laboratory. The selected proposals are from 14 institutions in nine states, with the total combined award amount of approximately $9.6 million during a four-year period. The MaterialsLab approach enhances the way researchers in government, industry and academia share information and promotes an open access approach to scientific data analysis and potentially guide hundreds of new, station-based scientific investigations.

For more information on the MaterialsLab program, visit