A diverse community of bacteria from a water sample is seen in this undated handout photo.(Xinhua/Reuters File Photo)

BEIJING, Sept. 25 (Xinhuanet) -- Germs become more deadly after making a trip in space, according to Tuesday's Proceedings of the National Academy of Sciences, U.S.

This was found by researchers of the Arizona State University's Biodesign Institue.

Researchers sent flasks of salmonella bacteria, best known as a culprit of food poisoning, and two other germs into space in 2006 with the Space Shuttle Atlantis. After they came back, the researchers found mice fed the space germs were three times more likely to get sick and died quicker than others which were fed identical germs kept on Earth.

Why does it happen?

Associate Professor Cheryl Nickerson of the university explained the reason as 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," she said.

"My expectation is that salmonella is not the only pathogen that could be impacted (by space flight)," said Nickerson.

Some germs might become stronger in space while others become weaker, she added, noting learning more about changes in germs has the potential to lead to novel new countermeasures for infectious disease.

(Agencies)