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Microbial transport at Yellowstone: by land, sea or air?

James E. Kloeppel, Physical Sciences Editor
(217) 244-1073;


Humans have a penchant for travel - driving, sailing and flying over the planet in search of new places to live. So do microbes, say researchers at the University of Illinois who have been studying microbial transport at Mammoth Hot Springs in Yellowstone National Park.

"Hot springs comprise a complex ecosystem of interacting microbes, geochemistry and mineralogy," said George Bonheyo, a postdoctoral researcher at the UI. "The rapid precipitation of calcium carbonate results in shifting flows, and in the sealing off of some springs and the eruption of new vents. But the source of the microbes, and the means by which they colonize new springs, has remained unknown."

To study the possible origins of microbial populations, Bonheyo and his colleagues - geologist Bruce Fouke, microbiologist Abigail Salyers and students Beth Sanzenbacher and Janki Patel, all of the UI - first collect water, rock and air samples from the hot springs environment. Then they use the sensitive polymerase chain reaction to detect the presence of microbes in the samples.

Microbes may roam the Yellowstone countryside by many means, Bonheyo said. They might raft the waters that feed the springs. They might fly on droplets of steam rising from active vents or on bits of sediment blowing from dried springs. They might even hitchhike on the feet of bison, birds or other animals moving from one spring to another.

"Where an established spring runs into a new source, the microbes may be directly transported by the runoff of the older spring," Bonheyo said. "But when a new spring erupts upstream of, or in isolation from other vents, the method of transport is not clear."

For example, during field measurements conducted earlier this year, five new springs erupted at Angel Terrace, a part of the Mammoth Hot Springs complex where the deposition of calcium carbonate occurs very rapidly. Bonheyo monitored the springs to observe the process of microbial colonization.

"This was a unique opportunity to sample water from a vent system that wasn't actively growing bacteria before," Bonheyo said. "While we did find evidence of life in the new springs, additional work will be required to conclusively trace its origin."

The microbes may have been present in the subterranean source waters before percolating to the surface, or they may have hitched a ride on the steam arising from surrounding springs.

To test the latter possibility, Bonheyo and his colleagues condensed steam from a nearby active vent on sheets of sterilized foil. In the resulting liquid, the researchers found the same microbes that live in the hot spring. "Whipped by winds, these microbes could be transported for hundreds of miles, or even globally," he said. Bonheyo presented the team's recent findings at the annual meeting of the Geological Society of America, held Nov. 9-18 in Reno, Nev. The work was sponsored by a UI Critical Research Initiatives grant.