There is a natural tendency, particularly among the general public, to view microbial mutations and evolution in a negative light. We associate changes in microbes with increased infectivity and virulence. We’ve got Hollywood and some pop-science books to thank for that misconception. When you throw bacteria from outer space into the picture, things get even grimmer. Reality tends to be less sensational. Microbes adapt to their environment to increase survival, no more, no less.
Ever since man first ventured beyond the outer regions of earth’s atmosphere, there have been bacteria and viruses in space. They’ve hitched rides on rockets, landers, clothing, and astronauts’ skin. And with the International Space Station in constant use for over twenty years, it’s safe to say, there’s a fair share of microorganisms to be found there. It’s also a certainty that they’ve evolved to maximize their changes of living long enough to reproduce.
SCIENTIFIC INQUIRER: First, can you describe the microbe situation on the International Space Station? How prevalent are microbes?
RYAN BLAUSTEIN: We carry our microbes everywhere, dropping some off and picking up others along the way. In the ISS, like other indoor spaces, we find human-associated microbes on surfaces and in dust. We are mostly concerned about the ones that can cause disease or damage building materials. However, most bacteria aboard the ISS (and everywhere) are non-harmful.
SI: What conditions did scientists believe would act as the most potent stressors?
RB: Bacteria in the ISS face a combination of stressors from spaceflight (e.g., microgravity, radiation) and from living on surfaces away from human hosts (e.g., dry conditions, limited resources, chemicals from cleaning products). Although spaceflight undoubtedly impacts microbial activity, our findings suggest the selective pressures from switching to an indoor lifestyle are probably just as important, if not more, for the ISS bacteria.
SI: How did you design your study?
RB: To see how bacteria may adapt to the indoors, we compared genetic data from 30 studies for clues about differences based on where they come from and type of lifestyle, such as being in indoor spaces vs. on humans or in soil.
SI: What were your findings?
RB: Bacteria living on surfaces and dust in the ISS have various capabilities to help cope with their environment, such as ability to repair themselves, scavenge for resources, and deal with temperature shock. These functions do not directly impact human health. The ISS bacteria did not have any special antibiotic resistance or virulence genes, which would have been concerning.
SI: From the current microbes on the ISS, are there any that are causes for concern?
RB: Absolutely. Although ISS bacteria are not mutating to become antibiotic-resistant or cause disease, it is still important to be proactive to minimize health risks. In space your immune system becomes weaker and you are completely isolated. In fact, previous studies indicate microgravity may enhance bacterial growth and virulence. Thankfully, astronauts are very healthy, so pathogens are probably absent or at least rare aboard the ISS. Germ transfer in confined spaces, like in hospitals or airplanes, has dire consequences. We need to continue taking appropriate precautions during space travel.
SI: In terms of superbugs, has anyone tested the effects of the use of antibiotics in space environments, e.g. larger spaces like the ISS or smaller confined spaces?
RB: Of the bacteria we looked at, we didn’t see any superbug characteristics. Nevertheless, the overuse of antibiotics and anthropogenic chemicals in medicine and agriculture has driven the rise of superbugs in hospitals and other confined spaces.
SI: In theory, the bacteria in the ISS and on astronauts’ bodies undergo changes at some point. When the astronauts return, presumably they are bringing some back to earth. Has anyone studied them?
RB: Yes, bacteria in the ISS and on astronauts’ bodies may change under selective pressure over time. Our genomic-based study and several others focused on isolates of bacteria that were brought back from the ISS. We are not aware of studies on the human microbiome after space travel.
SI: What’s next for you?
RB: Getting out into the “field” would be nice. We will continue to focus on microbial evolution in the environment. Our primary interest is the interactions between the microbiome and drugs, like antibiotics.
MAIN IMAGE SOURCE: NASA
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