Salmonella germs that went into space on a 2006 mission returned three times more deadly, reports the AP. Space travel altered 167 genes in the germ, which is the leading cause of food poisoning, and it killed mice at much higher rates than identical samples left on Earth. The Earth-bound germs killed 60% of mice within 25 days; their space-traveling counterparts claimed 90%.
Researchers aren't sure why, but they theorize that the cells were responding indirectly to microgravity. "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," said one researcher, adding that the experiment could lead to novel countermeasures for infectious disease.