Bacteria, Fungi Hitch Rides on Desert Dust Across Atlantic

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Bacteria, Fungi Hitch Rides on Desert Dust Across Atlantic

Monday, June 05, 2006

FOX News

By Bjorn Carey

http://www.foxnews.com/story/0,2933,198241,00.html

Dust clouds blowing across the Atlantic Ocean carry hidden pathogens

that might reach the United States.

While the dust itself can cause respiratory stress, scientists have

now confirmed that clouds originating in Africa carry microbial life

that can cause disease in humans, plants and other animals far from

the source.

Desert dust storms whip up and disperse an estimated 2.4 billion

tons of soil and dried sediment throughout the Earth's atmosphere

annually.

" Since a gram of desert soil may contain as many as 1 billion

bacterial cells, the presence of airborne dust should correspond

with increased concentrations of airborne microorganisms, " said Dale

, a scientist with the U.S. Geological Survey.

and his colleagues presented their latest findings last

month at the 106th General Meeting of the American Society for

Microbiology in Orlando, Florida.

Entering dust storm season

During the African dust storm season, which runs May to October,

strong winds in the Sahara Desert kick up major clouds of dust that

can drift across the Atlantic Ocean in just a few days.

Some of the dust settles in the ocean, but a large amount dumps on

Caribbean islands and the southeastern United States, particularly

Florida.

" On the Florida coast you might wake up and see what we call

a 'tequila sunrise,' " said, referring to Florida's fiery

sunrises. " Well, that orange is African dust. "

Traces of African dust have been discovered as far west as New

Mexico. The western states are also the recipients of dust that's

been stirred up in China's deserts and blown across the Pacific.

Previous studies in Korea and Trinidad have reported that citizens

experience more respiratory stress and visit the emergency room with

respiratory problems more frequently following such storms,

said.

But researchers consider the tiny microbes — mainly bacteria and

fungi — that get caught up in these dusty gales as an even greater

concern.

Microbes in the mix

Historically, scientists believed that several days of ultraviolet

light exposure would kill off any microbes traveling in dust clouds.

Yet when and his colleagues screened air in the middle of

the Atlantic Ocean, they found viable airborne microbe populations.

On 24 of the 40 sampling days during May and June 2003, they

collected viable amounts of bacteria and fungi. The three highest

sample returns were collected during the two highest periods of dust

activity as determined by the U.S. Navy's Naval Aerosol Analysis and

Prediction System Global Aerosol Model.

The researchers found pseudomonas aeruginosa bacteria, a microbe

that causes ear infections, and kocuria bacteria, which can cause

mouth lesions, in the mix of microbial life.

" It doesn't matter where we do the research — we typically identify

20 to 30 percent of the microbes in dust clouds as known pathogens

to some animal on the planet, " told LiveScience.

DNA analysis matched two of the airborne substances 100 percent to

dust-borne samples previously collected in Mali, a landlocked

country in Western Africa.

One of them, a known human pathogen, has also been found mixed in

with African desert dust while blowing around the U.S. Virgin

Islands.

Additional analysis identified a number of bacteria and fungi that

cause disease in animals and plants, including one responsible for

damaging Florida sycamore trees.

" It is tempting to speculate that transatlantic transport of dust

could be a vector to renew reservoirs of some plant and animal

pathogens in North America and could also be the cause of new

diseases, " said.