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Member Spotlight: Stefan Green

The Impact of Space Flight on Gut Microbiomes: A Study

Becoming a scientist or an astronaut are among the dreams of many children – and some adults.  However, when you become a scientist and have the pleasure to work with NASA and astronauts, your job escalates into a great ice-breaking conversation. That is exactly what happened to Stefan Green, Ph.D, Core Director of the DNA Services Facility at the University of Illinois at Chicago. Literally, this opportunity came to him because he ran a core facility. A centralized research operation that affords him the opportunity to see a variety of projects come through his door.  This one took him to another atmosphere. 

Through his role he was brought samples from Dr. Ali Keshavarzian’s Lab at Rush University, a few blocks away. The Keshavarzian lab is interested in, among other things, the effect of disrupted circadian cycles on gut microorganisms, both in experimental mouse studies and in humans. And, by way of a colleague of Dr. Keshavarzian’s at Northwestern (Dr. Fred Turek, Director of the Center for Sleep and Circadian Biology), Stefan became involved in NASA-funded research into effects of space flight on gut microbes. NASA had become interested in circadian and gut research, since while in space astronauts do not sleep well. A real problem when trying to work on high-end equipment, research, and operate a space station in a zero gravity environment. 

NASA recently had an unusual opportunity to study the effects of spaceflight on twin astronauts. The identical twin brothers Mark and Scott Kelly, both astronauts with extensive spaceflight experience, volunteered themselves for a remarkable study. Scott spent nearly a year (340 days) on the International Space Station, while his brother Mark remained on Earth. Samples were taken before, during, and after spaceflight from both twins, and once the samples were collected, Stefan’s lab analyzed the microbiome of both twins at all time points.  In general, astronauts face a lot of stressors compared to us Earth-dwelling folk.  In part due to microgravity experienced on the ISS, life in the space environment is quite different than life on Earth, and this can lead to changes in biology, including difficulty sleeping. All of these changes can also have an impact on gastrointestinal health, which is very important when considering long-term flights. Why?  Well, for one thing – because we humans want to travel to the planet Mars. To get to Mars, astronauts will need to endure longer amounts of time in space for travel and sleep.  We definitely want them to sleep, and we want them to have healthy gut microorganisms. So the microbiome studies will help scientists and NASA to understand what effects space flight have on gut microorganisms, and ultimately, how modifications in the astronaut’s diet can be made to ensure that the gut is healthy, regardless of the amount of sleep the astronauts get.

One limitation of this study is that there is only one set of twins. But, given that there are relatively few astronauts, there is a limit to how many twins can be used for such studies. Thus, researchers have to look at the microorganisms over time to see how spaceflight changes gut microorganisms, whether those changes are permanent, and what conditions of spaceflight are the most responsible for the changes. Future studies, however, are planned with mice – and with these animals it is much easier to get a larger number of participants!

Aside from space, astronauts, and science, the microbiome is a pretty cool thing.  It goes beyond sequencing poop, I mean stool, samples.  It can help to personalize medicine.  We all eat different things, thus changing the diversity and composition of bacteria and viruses in our gastrointestinal tracts. Although we can control what goes into our bodies and we can measure what comes out, there are many areas within that are not easily accessible. However, the promise of personalized medicine suggests that for each individual, a specific diet may improve health by altering or maintaining our gut microorganisms.

Green and his collaborators found a modest, but significant, change in the microbiome of Scott Kelly during his time in space. Once he returned to our planet, his microbiome returned to pretty much what is was before he left. Another promising finding was that the diversity of microorganisms – the number of different types of bacteria – did not appear to be altered by spaceflight. We are going to need to keep our diverse microorganisms with us when we travel in space for much longer time periods!

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