http://news.yahoo.com/s/ap/germs_in_space

Spoiler Alert, click show to read: 
...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...."

Aw. Does this mean we shouldn't explore into space too often?
Maybe we could clean out the germs on space travelers with radiation, freezing temperature, or a hot spring bath.