'Superbugs' Could Benefit Humans

That virulence could pose real risks to astronauts, but those earlier findings were obtained under artificial conditions whose medical relevance remained uncertain. They came from a device resembling a small Ferris wheel, which gently swishes bacteria upward in a liquid medium and so gives them the sensation of weightlessness. Scientists call it a low-shear environment, because the bacteria do not fall through the liquid but remain suspended, as though floating in outer space.

If real weightlessness also increases bacterial virulence, then space food might need to be better screened for pathogens and stronger antibiotics might be needed to treat infections in space.

In Nickerson's experiment, astronaut Heidemarie Stefanyshyn-Piper grew salmonella bacteria, which can cause food poisoning, and preserved them for subsequent tests upon the shuttle's return.

Back on Earth, the space-grown bugs were fed to mice. They proved to be nearly three times as likely to cause disease and about twice as deadly as they were before the flight, the team reports in this week's online edition of the Proceedings of the National Academy of Sciences, released yesterday.

Tests found 167 genes that were either more or less active in the shuttle bugs than in their earthbound counterparts -- including many under the control of a single genetic regulator called Hfq.

"This is really the first time that, under actual conditions of outer space, increased virulence and specific changes in gene regulation have been demonstrated," said A.C. Matin, a molecular biologist at the Stanford medical school.

The finding is worrisome because spaceflight is known to suppress astronauts' immune systems, Matin said. Unfortunately, he added, NASA has cut funds for studies of this safety issue, a decision he equated to "playing Russian roulette with people in space."

The work offers potential benefits for non-astronauts, too, Nickerson said. Tissues that are relatively isolated from the fluidic turbulence of the body's interior, including parts of the gastrointestinal and urinary tracts, are low-shear environments, it turns out -- perhaps explaining why infections there are often hard to treat. Nickerson suspects that drugs designed to act on Hfq could offer a new approach to fighting such infections.

A second study, described in the October issue of Radiation Research, involves single-cell organisms known as archaea, which share some traits of bacterial and human cells.

It started at the Idaho Accelerator Center at Idaho State University in Pocatello, where scientists are developing a device that shoots extremely high-energy beams of electrons capable of killing every kind of known microbe.

They hope to make a portable device that can quickly make an area safe after a bioweapon attack.

Scientists have long been aware that some bacteria are remarkably resistant to radiation. The most resilient of all, Deinococcus radiodurans, grows happily while basking in gamma-ray doses of 5,000 grays, hundreds of times as high as a common E.coli bacterium can handle. (One gray is the amount of radiation in about 5,000 chest X-rays.)