Compared to bacteria that remained on earth, the space-traveling Salmonella had changed expression of 167 genes. After the flight, animal virulence studies showed that bacteria that were flown in space were almost three times as likely to cause disease when compared with control bacteria grown on the ground.
Oh, this is EVIL. Take something a little more dangerous than Salmonella up there, and bring back hyper-typhoid or hyper-tuberculosis or hyper-syphilis or even (if you wanted to branch out, perhaps, and try for viruses) hyper-influenza back to Earth. It would make Black Death and the Spanish Flu Pandemic look like walks in the park.
And we thought that the Andromeda Strain was science fiction...