GOING to space changes a person. But humans aren't the only space travellers we need to consider: microbes can change after just a few days without gravity. Now scientists worry that the bugs astronauts bring with them in their guts may turn traitor in space.
The human body isn't just one organism, but an entire community teeming with millions of microbes, so there's a whole community of new questions that spacefarers need to think about. In a report released last week, scientists at the US National Academies highlighted the extent of our ignorance about the way microbes behave in space, and how best to treat astronauts who get sick. The report cited studies showing that Salmonella typhimurium, known for causing food-borne illness, can change its genome to become more virulent after just a few days in space. And studies have also shown that spaceflight can shorten the shelf lives of medications.
In the past decade or so, scientists have realised the importance of the millions of microbes humans carry around internally, called the microbiome, to our well-being. Microbes outnumber human cells in the body by 10 to 1, and many perform vital functions that keep us healthy, like helping digest our food and monitoring our immune system.
"We function largely within the context of our microbiome," says Cheryl Nickerson of Arizona State University in Tempe, who has studied spacefaring Salmonella. "But we know essentially nothing about how spaceflight affects not just the pathogens but also the body's microbes."
To help clear things up, a project called Astronaut Microbiome is currently flying on the International Space Station. A team led by Hernan Lorenzi at the J. Craig Venter Institute in Rockville, Maryland, will take saliva, blood and stool samples from nine astronauts before, during and after a six-month stint aboard the ISS to find out what actually happens to their microbiome in space. The team suspects that astronauts may lose certain microbes that they rely on to stay healthy, leaving them more susceptible to opportunistic infections.
While Lorenzi's team investigates inside the human body, others remain focused on the microbes fighting to get in. Last week, an experiment blasted off for the ISS aboard the Cygnus space capsule to test whether E. coli can survive higher levels of antibiotics in microgravity than it can on Earth. And in June, Nickerson will launch a new experiment to infect roundworms with Salmonella while they are in space, to see the disease take its course without gravity.
These questions are especially important now that space agencies are planning to make longer trips than ever before. On 8 January, NASA won US presidential approval to extend the space station's lifetime until at least 2024, four years past its original end date. Starting next year, two men will live on the ISS for a full year, the longest mission of any NASA astronaut in history. And private initiatives have attracted the attention of plenty of wannabe astronauts.
"We all have our eye on sending people to Mars or to an asteroid or to the moon for a long period of time," says Mark Shelhamer, chief scientist at NASA's Human Research Program. "The question is, what happens when you send someone?"
In the end, though, space travel may mean accepting some gaps in our knowledge. "Would a trip to Mars be riskier than what we've done in previous space missions? Absolutely," says Jonathan Clark, chief medical officer for the Inspiration Mars Foundation, a private venture aiming to send two astronauts around the Red Planet in 2018. But there is always somebody willing to go, he says.
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