Germs
taken into space can come back stronger than before
By RANDOLPH E. SCHMID
AP Science Writer
WASHINGTON (AP) - Scientists wanted to see how space travel
affects germs so they put some carefully wrapped Salmonella,
best known as a culprit of food poisoning, aboard a space
shuttle in September 2006.
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 to space.
Why?
"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 effects."
"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.
___
On
the Net:
Proceedings
of the National Academy of Sciences: http://www.pnas.org
