'Superbugs' Could Benefit Humans

Cheryl Nickerson of Arizona State University designed an experiment that showed spaceflight increases the virulence of common bacteria. (Biodesign Institute At Arizona State University)

To see if that represents a natural limit of what a cell can handle, Linda C. DeVeaux of Idaho State, Shiladitya DasSarma of the University of Maryland Biotechnology Institute in Baltimore and co-workers took cultures of an archaeon called Halobacterium and exposed it to the 20 million-electron-volt Idaho beam four times over four months.

"We zapped the hell out of them," DeVeaux said.

The mutant microbes that survived that experiment are unfazed by doses exceeding 11,000 grays, putting them well into first place for radiation hardiness among actively replicating organisms.

But the achievement is about more than a place in the Guinness World Records book, DasSarma said. Tests have revealed the molecular mechanism that appears to grant the new mutants much of their hardiness -- a mechanism that, in a weaker form, protects and repairs DNA in human cells, too.

With that target identified, there is hope of developing medicines that enhance those natural mechanisms in human cells. Supplied to healthy tissues, they could minimize "collateral damage" in cancer patients who get radiation therapy.

Such drugs may also someday protect astronauts from the high radiation doses they would receive during prolonged spaceflights, DasSarma said. More controversially, he added, the work suggests that halobacteria or other microorganisms can survive cataclysmic radiation events in space and still land alive on Earth aboard meteorites.

John R. Battista, a microbiologist at Louisiana State University in Baton Rouge, said blasting bugs with beams and studying their genes "offers an entirely new approach to studying radio-resistance in organisms."

That is important, he said, because although halobacteria are not known to cause disease, some medically threatening microbes may share their capacity to adapt when stressed -- something biodefense beamers would want to know before they start mopping up.