Post by Chicago Astronomer - Astro Joe on Sept 25, 2007 23:12:17 GMT -6
Germs Taken to Space Come Back Deadlier
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.
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."
"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.
Source: hosted.ap.org/dynamic/stories/G/GERMS_IN_SPACE?SITE=DCUSN&SECTION=HOME&TEMPLATE=DEFAULT