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Microbes Hitch Rides on Dust Plumes From Asia to North America, Study Finds

Dec 19, 2012 06:31 AM EST
Microbes dust plumes
Plumes of dust, one in April and the other in May 2011, originated in Asia and traveled west – high in the troposphere – across the Pacific Ocean to the West coast where they were detected by an observatory in central Oregon. Scientists used models to determine the back trajectories.
(Photo : University of Washington)

A large number of microbes are hitching a ride through dust plumes in the upper troposphere, from Asia across the Pacific Ocean and land in North America, according to a new study.

Researchers from University of Washington analyzed samples of two large dust plumes that appeared in April and the other in May 2011, at Mount Bachelor in the Cascade Mountains of central Oregon. Unlike using traditional methods of culturing to analyze the samples, the research team gathered biomass in the form of DNA to apply molecular methods to the samples.

They detected more than 2,100 unique species of microbes compared to 18 found in the same dust plumes using the traditional culturing method back in July.

According to the researchers, about 7.1 million tons (64 teragrams) of aerosols - dust, pollutants and other atmospheric particles, including microbes - travel across the Pacific each year from Asia to North America.

These aerosols are carried by wind storms in the upper troposphere, which is the lowest layer of the Earth's atmosphere. Almost all our weather takes place in the troposphere.  

Half of the microorganisms carried by windstorms are bacterial, while the other half is fungal. These species of microbes were either dead on arrival or harmless to humans. Most of them can be found in low, background levels on the West Coast, but the dust plumes increased the levels of microbes. This made scientists link microbes to air pollution, which are present in the background but can reach elevated levels during particular events, reported LiveScience.

"I think we're getting close to calling the atmosphere an ecosystem," David J. Smith, lead author of the study from University of Washington, said in a statement. "Until recently, most people would refer to it as a conveyor belt, or a transient place where life moves through. But the discovery of so many cells potentially able to adapt to traveling long distances at high altitudes challenges the old classification." 

According to Smith, two of the three most common families of bacteria have the ability to form spores to help them hibernate in harsh conditions and make them well-adapted to travel longer distances at high altitudes.

Microbes can also become the nucleus of rain drops and snowflakes and influence the amount of precipitation that falls when they interact with their high-altitude environment. However, scientists have not witnessed the growth of microorganisms at higher altitudes.

They are further planning to study how the microbes interact with harsh conditions during high altitude transports. But such efforts will face a lot of challenges as it is very difficult to get samples from the upper troposphere, the researchers said.

The findings of the study, "Free Tropospheric Transport of Microorganisms from Asia to North America", are published in the current issue of the journal Applied and Environmental Microbiology.

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