Lethal Bacteria Turn Deadlier After Space Travel

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Nickerson and colleagues, whose study appears online in today's Proceedings of the National Academies of Sciences, have tested bacteria in a variety of harsh environments. (See related: "NASA 'Clean Rooms' Brimming With Bacteria" [September 7, 2007].)

"In the last few decades, huge leaps of knowledge have been made when we test biology in extremes," she said.

"Situations where it is very hot, very acidic, or low oxygen have taught us an enormous amount about how cells respond to those environments, and from that we've made huge advances in biotech and bioengineering."

All About the Fluids

It's not lower gravity that makes bacteria deadlier in space.

The key environmental change is a mechanical force known as fluid shear, or the motion of fluid around a cell.

In human gastrointestinal tracts, this current slows down or even stops, creating an area of low fluid shear. These environments allow bacterial infections to flourish. Space is also a low-shear environment.

"Fluid shear ... is an environmental signal that had been overlooked for quite a while," Nickerson said.

That's because ground-based techniques can't replicate accurate fluid shear environments.

But in space, scientists can control fluid shear far better than in any Earth-based lab.

Deep Impact

By understanding the role of fluid shear on the evolution of disease-causing bacteria, scientists hope to offer better techniques to fight disease on Earth. (Listen and learn how to avoid dangerous foods.)

David Niesel, chair of microbiology and immunology at the University of Texas at Galveston, was not involved in the study.

"[The study] is a nice piece of work. It shows an increase in virulence in an animal model and a molecular mechanism that could account for that," he said.

"Anything we learn about how bacteria respond to new environments and their virulence mechanisms may help us understand how these organisms cause disease, and that gives us new opportunities to come up with therapeutics to combat disease on Earth."

Understanding how bacteria alter themselves in space will be especially important for future long-term missions, such as colonization of the Moon or a manned mission to Mars. (Related news: "New Space Shield May Help Make Mars Mission Reality" [March 23, 2007].)

"What happens in microgravity at the cellular level is not really well understood," said Steve Maclean, a Canadian astronaut and crew member on the 2006 Atlantis shuttle that housed the experiment.

Since bacteria are always present inside humans, it is impossible to prevent any of the organisms from getting into the space shuttle.

"Given that bacteria survive better and our immune system is functioning at a lower level, does this increase your risk of infection?" Maclean said.

"It's something to think about before we go to Mars."

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