Germs sent into orbit on the space shuttle last year came back to Earth three times more virulent, a finding that could have major implications for astronauts on the international space station or on proposed voyages to the moon and Mars.
Researchers knew that space travel depressed astronauts' immune systems, so the observation that infectious agents can become more pathogenic in space could lead to new sterilization requirements for food and other items, as well as to new protocols for the treatment of infections during missions, experts said.
The findings could have relevance for humans on Earth because the bacterium in question is common and can have severe consequences, said Cheryl Nickerson, a microbiologist at Arizona State University, who led the experiment.
Nickerson and her colleagues sent vials of the bacterium "Salmonella typhimurium, " which is implicated in many food-poisoning outbreaks, into space aboard the shuttle Atlantis in September 2006.
Control bacteria were grown at the Kennedy Space Center in Florida under identical conditions - except for the presence of gravity.
When the bacteria returned to Earth, they killed 40 percent of the mice into which they were injected.
The bacteria from the Kennedy Space Center killed 10 percent of the mice. When the team examined the space bacteria, they reported Tuesday in the Proceedings of the National Academy of Sciences, they found that the expression of 167 genes had been altered by the spaceflight.