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ORNL's scientists explore microbes' role in global warming For clues to the environmental effects of climate change and keys to perhaps offset its repercussions, ORNL's Christopher Schadt is going, literally, underground. Schadt studies microbes, tiny living organisms that inhabit every inch of ground we live on and whose job it is to carry out important duties such as decomposition, soil respiration, nitrogen fixation and nutrient delivery to plants. Microbes also impact carbon storage in soils by transforming carbon in decaying plants into other forms of organic matter—a matter of great interest to climate change research. Thus, these little creatures—seen only with the aid of a microscope—are very big players in determining both the impacts of climate change and our response. The thing is, Schadt says, much about the identity and function of microbes remains a mystery. That is because growing microbes in a laboratory setting is difficult, and identifying them in nature, until recently, has been nearly impossible because within one gram of soil typically lives thousands of species of bacteria. "Soil is probably the most diverse environment on earth," says Schadt. "When you pick up a handful of soil there are so many different microbial communities. It's just full of organisms." To tap into the "black box" of microbial function underground, Schadt and other researchers are adapting modern molecular tools to the needs of microbial ecology. This includes using microarrays, powerful technology that allows simultaneous measurement of gene expression under particular conditions for up to tens of thousands of genes at a time, and other techniques to help determine the function of microbes in nature at a cellular level. First, Schadt says, scientists hope to answer the basic questions of "What organisms are present in the soil? and How do they function?" Ultimately, that information will be tied into models projecting how ecosystems could respond to the various expected results of climate change, such as higher temperatures, changes in precipitation and, of course, higher levels of carbon dioxide in the atmosphere. Ultimately, the work could help determine the role of microbes in mitigating climate change or helping ecosystems adapt in response to climate change. For example, Schadt is involved in a project of the Department of Energy's Carbon Sequestration in Terrestrial Ecosystems program, or CSiTE (csite.ornl.gov), at a University of Tennessee site in the western part of the state that is studying microbial activity in a field of switchgrass, a potential bioenergy crop. Researchers are hoping to understand how large plantings of crops for bioenergy could influence carbon sequestration in the soil and, thus, potentially help mitigate climate change. "Can you actually influence carbon storage?" says Martin Keller, director of ORNL's new BioEnergy Science Center and microbiologist himself. "Do you think you could engineer an environment to store 100% more carbon? We don't know, and we don't know what the potential implications of that might be. It could completely change the balance of the soil." But Keller says the new tools now available "will enable us to go to the next level. The opportunity is in all these new technologies."—Larisa Brass
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