Germs Taken to Space Come Back Deadlier
It sounds like the plot for a scary B-movie: Germs go into space on a
rocket and come
back stronger and deadlier than ever. Except, it really happened.
The germ: Salmonella, best known as a culprit of food poisoning. The
trip: Space Shuttle STS-115, September 2006. The
reason: Scientists wanted to see how space travel affects germs, so
they took some along — carefully wrapped
— for the ride. The result: Mice fed the space germs were three
times more likely to get sick and died quicker than
others fed identical germs that had remained behind on Earth.
"Wherever humans go, microbes go, you can't sterilize humans. Wherever
we go, under the oceans or orbiting the earth, the
microbes go with us, and it's important that we understand ... how
they're going to change," explained Cheryl Nickerson, an
associate professor at the Center for Infectious Diseases and
Vaccinology at Arizona State University.
Nickerson added, in a telephone interview, that learning more about
changes in germs has the potential to lead to novel new
countermeasures for infectious disease.
She reports the results of the salmonella study in Tuesday's edition of
Proceedings of the National Academy of Sciences.
The researchers placed identical strains of salmonella in containers
and sent one into space aboard the shuttle, while the
second was kept on Earth, under similar temperature conditions to the
one in space.
After the shuttle returned, mice were given varying oral doses of the
salmonella and then were watched.
After 25 days, 40 percent of the mice given the Earth-bound salmonella
were still alive, compared with just 10 percent of
those dosed with the germs from space. And the researchers found it
took about one-third as much of the space germs to kill
half the mice, compared with the germs that had been on Earth.
The researchers found 167 genes had changed in the salmonella that went
"That's the 64 million dollar question," Nickerson said. "We do not
know with 100 percent certainty what the mechanism is of
space flight that's inducing these changes."
However, they think it's a force called fluid shear.
"Being cultured in microgravity means the force of the liquid passing
over the cells is low." The cells "are responding not to
microgravity, but indirectly to microgravity in the low fluid shear
"There are areas in the body which are low shear, such as the
gastrointestinal tract, where, obviously, salmonella finds itself,"
she went on. "So, it's clear this is an environment not just relevant
to space flight, but to conditions here on Earth, including in
the infected host."
She said it is an example of a response to a changed environment.
"These bugs can sense where they are by changes in their environment.
The minute they sense a different environment, they
change their genetic machinery so they can survive," she said.
The research was supported by the National Aeronautics and Space
Administration, Louisiana Board of Regents, Arizona
Proteomics Consortium, National Institute of Environmental Health
Sciences, Southwest Environmental Health Sciences
Center, National Institutes of Health and the University of Arizona.
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