Salmonella in Space

Via GeekPress, among others: The AP reports on the B-movie salmonella that came back deadlier after its trip on the space shuttle:

After 25 days, 40 percent of the mice given the Earth-bound salmonella were still alive, compared with just 10 percent of those dosed with the germs from space. And the researchers found it took about one-third as much of the space germs to kill half the mice, compared with the germs that had been on Earth.
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."
However, they think it's 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."