Plumes of dust deliver vast quantities of microbes such as bacteria from Asia to North America, according to a new study from the University of Washington.
“We detected thousands of unique microbial species, many of which seem particularly well-suited for atmospheric transport,” says study author David J. Smith, from the University of Washington, Seattle. “We also detected archaea, a domain of life that has never before been sampled at high altitude. We are just starting to understand the consequences of long-range microbial transport.”
“The long-range transport and surprising level of species richness in the upper atmosphere overturns traditional paradigms in aerobiology,” explains Smith.
“Over 70 million tons of Asian aerosols—mostly dust—reach our continent every year,” says Smith. “There could be thousands of microbes per gram of dust.”
Smith foresees value in understanding how bacteria survive at high altitudes during intercontinental journeys.
For example, identifying the mechanisms for resisting ultraviolet radiation at altitude, which likely involve protecting and repairing DNA, could prove invaluable to biotechnology and medicine, says Smith.
“It’s a small world. Global wind circulation can move Earth’s smallest types of life to just about anywhere,” Smith said.
The research took place at an observatory on the summit Mt. Bachelor in the Pacific Northwest. Mount Bachelor, like many other mountains in the Cascades, has a peak tall enough to pierce the upper troposphere “We could process huge volumes of air, 24/7, and capture enough biomass to analyze airborne microorganisms using molecular methods,” Smith explained.
Two major pollution events emanating from Asia during the sampling season of 2011 helped the team distinguish Asian expatriate microbes from locals, along with chemical and meteorological methods.
The research was physically challenging. “Mt. Bachelor is a very snowy place and one of the windiest mountains in North America,” says Smith. “Some summit days were an endurance marathon.”
D.J. Smith, H.J. Timonen, D.A. Jaffe, D.W. Griffin, M.N. Birmele, K.D. Perry, P.D. Ward, M.S. Robert, 2012. “Intercontinental dispersal of bacteria and archaea in transpacific winds.” Appl. Environ. Microbiol. (E-pub ahead of print 7 Dec. 2012.
Funding for the work came from the National Science Foundation, National Geographic Society, NASA’s Astrobiology Institute, the UW’s NASA Space Grant Consortium and the UW Department of Biology.