Germs Can Travel the World by "Hitchhiking" on Dust

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"We found several species of bacteria and fungi … on the small particles," Broughton said.

The team was even able to cultivate and grow several of the microbes, proving that these microorganisms can remain viable for centuries.

Citing the harsh elements the microbes must endure, including severe weather and ultraviolet radiation, Broughton said he believes that only certain microbes can survive the trip.

"It's likely that only those bacteria and fungi that have protective structures, like spores, can survive the travels," he explained.

Microbes that dwell on arid rock and soil are better able to withstand the dryness and radiation that accompany intercontinental travel, he added. As a result, deserts are the only terrestrial environments where these traveling microbes can be found in abundance.

(Read related story: "Humans Wear Diverse 'Wardrobe' of Skin Microbes, Study Finds" [February 6, 2007].)

A Pathway for Disease?

The newly studied phenomenon begs the question: If bacteria and fungi can be carried on the wind from country to country, could disease travel the same path?

"Most normal human pathogens are not resistant enough [to survive the trip]," Broughton said.

"Unless there's some great change in the western Sahara, disease [traveling in this manner] doesn't pose a health threat."

While the spread of disease may not be an issue, scientists believe that the study confirms an important theory with global implications.

"We know very little about the longevity of microbes and their ability to tolerate long periods of stress," said Kenneth Timmis, head of the Environmental Microbiology Laboratory at the Helmholtz Centre for Infection Research.

The new study not only aids in scientists' understanding of how microbes survive, it also provides important evidence of how major atmospheric pathways influence the spread of microbial life on the planet, he said.

"This is a timely reminder that almost all parts of the biosphere connect," Timmis observed.

Broughton agreed: "This study means that the world is not an isolated place. In a microbiological sense, we are all part of one planet."

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