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Gary Franc, a University of Wyoming professor of plant pathology and microbiologist, is one of a growing number of scientists who believe that living microbes -- and not just dust -- are responsible for producing the ice crystals in clouds that end up in precipitation.
Franc's research, along with other scientists' similar work around the nation, is profiled in Discover Magazine's April 2012 issue cover story, "Life at the Edge of Space: Do High-Flying Microbes Control Earth's Weather?"
"The amount of different types of microbial life present in the cloud droplets that make up a winter storm are amazing," Franc says in the article. "There's a whole ecosystem going on in the clouds that's largely undefined."
For years, the conventional science was that mineral and soil dust, and perhaps soot particles, swept by the wind miles up into the clouds, formed ice crystals. These crystals, in turn, are the first seeds for forming rain, snow and hail.
Now, Franc and other scientists are gaining attention for their research, some of which goes back decades. The research recognizes that bacteria and other microbes are thriving thousands, and even tens of thousands, of feet up in the wild blue yonder. This realization that the atmosphere is more biologically diverse than once thought casts a new light on how weather patterns occur and their potential effect on crop production and harvest, and groundwater recharge.
"You have this whole chain of downstream effects. That's why I think there is so much burgeoning interest in this," Franc says. "People are seeing linkages, that there are many potential ramifications of complicated bioprocesses. Bacteria have a profound influence on our lives that we are barely scratching the surface at understanding."
Franc's interest in this ‘bacteria-in-the-clouds" theory goes back decades. Coincidentally, it was influenced deeply by UW researchers who came before him. In the mid-1960s, Gabor Vali, a Hungarian-born doctoral student and future UW professor, was studying physics at McGill University in Montreal. Vali devoted his research to learning what unknown particles in clouds allowed ice to be nucleated at warmer temperatures and create rain or snow, according to the Discover article. During his experiments, Vali froze drops of rainwater or snow, which froze at different temperatures, based on what kinds of microbes were inside the droplets.
At the time, most scientists were testing droplets in clean and sterile environments. According to the Discover article, Vali decided to test muddy snow he collected from under his children's swing set. He soon learned that the contaminated snow froze at 23 degrees Fahrenheit much more often than his clean samples. When Vali added rotting leaves to his experiment, the snow froze at 28 degrees Fahrenheit -- the warmest temperature at which he had seen drops freeze, according to the article. In 1972, UW graduate student Richard Fresh identified a bacterium -- Pseudomonas syringae - in rotting leaves that triggered the ice.
"The science evolved, in my mind, from some of the early researchers -- Gabor Vali and Leroy Maki at UW -- who found that some bacteria could be found in some of the ice nuclei," Franc says. "It's a coincidence I ended up here (at UW)."
At the time of Vali's discovery, Franc was an undergraduate student at the University of Wisconsin-Madison, where doctoral student Steven Lindow -- independent of Vali and Fresh -- discovered P. syringae's ability to nucleate ice at warm temperatures.
During his college plant pathology course, Franc says one of Lindow's co-workers demonstrated ice-nucleating bacteria by triggering freezing.
"It really piqued my interest," Franc recalls. "I wondered, ‘For what reason would bacteria cause ice to form?' What was the evolutionary pressure for that?"
As a doctoral student at Colorado State University, Franc got an opportunity to learn more. There, he studied a potato pathogen called Erwinia caratovora.
"I found it (Erwinia) in irrigation water and traced it back to the ocean," Franc says. "I wondered if bacteria could be involved in weather and be transported in storm systems. I believe that is the case."
For his dissertation, Franc began stringing the clues together, starting with irrigation water used to water potato fields in Colorado. Through samples, he traced the potato pathogen to a nearby river and then to headwaters in remote areas of the Rockies.
"If it (Erwinia) was in the headwaters, I figured it must be in the snowmelt," Franc says. "I found it in snow. Snowpack comes from storm systems that come from the ocean. I found it in the ocean and rain."
As a professor, Franc later collaborated with Paul DeMott, a senior research scientist in Colorado State University's Department of Atmospheric Science. The two have worked together on a National Science Foundation-funded project for the past three years that centers on research studying biogenic nuclei in the atmosphere and looking for bacteria in precipitation.
"Paul and I thought about this for many years, and now it's becoming sexy for people to start thinking that microbes and biology can play a role in such a large process like storms and weather," Franc says. "The ice-nucleating part of the science is almost like a feeding frenzy. There is a lot to summarize and get out into the scientific community. We're gathering data faster than we can write."
"There are a handful of different bacterial species capable of initiating ice formation," he continues. "Although they each may be potentially involved in atmospheric precipitation processes, we have not determined the extent to which they are involved and have not determined if one species is more important to atmospheric precipitation processes compared to another. The research needs to be carefully conducted."
Gary Franc, a UW professor of plant pathology and a microbiologist, tests samples for bacterial ice nuclei in his lab.