In today’s Academic Minute, Dr. Jason Keller of Chapman University explains how organisms alter one of life’s most fundamental processes in oxygen-poor environments.
Jason Keller is an assistant professor of biological sciences in the Schmid College of Science and Technology at Chapman University in Orange, California. As an ecologist, Keller is broadly interested in the flow of carbon and nutrients through ecosystems and how ecosystems will respond to ongoing global change. His current research focuses on the controls of anaerobic decomposition and greenhouse gas dynamics in a variety of wetlands, ranging from northern peatlands to tidal marshes. He earned his Ph.D. at the University of Notre Dame.
Dr. Jason Keller – Bogs and the Carbon Cycle
When you flip on a switch, the resulting flow of electrons provides the energy necessary to turn on a light.
In much the same way, the flow of electrons through cells provides the energy necessary to sustain life. In human cells, electrons generally flow from organic matter (the food we eat) to oxygen (the air we breathe). The same flow of electrons is also important in the process of microbial decomposition.
When a leaf falls to the forest floor, microbes use this organic matter as a source of electrons. The electrons eventually find their way to oxygen, thus generating the energy the microbes need to survive. Things become even more interesting when you add water. In flooded environments like wetlands, oxygen is not readily available to accept the electrons flowing from organic matter. Under these anaerobic conditions, microbes “breathe” a variety of other substances in place of oxygen. For example, there are microbes that can breathe the compound sulfate (SO4). To see (or, rather, smell) this microbial process, take an egg out of your refrigerator and place it in the sun for a few days. The characteristic rotten egg smell is hydrogen sulfide, the end product of microbes moving electrons from organic matter to sulfate.
Other microbes can “breathe” forms of nitrogen; carbon dioxide; and even solid metals, including iron and manganese. Recently we’ve discovered that some microbes can actually “breathe” organic matter in place of oxygen. Students in my laboratory have demonstrated that microbes moving electrons from one form of organic matter to another dominate decomposition in some wetland soils.
The decomposition of organic matter using these alternative electron acceptors is generally slower than it would be if oxygen were available. At the global scale, this inefficiency has resulted in wetlands storing roughly 75-times the amount of carbon released annually from fossil fuel burning in their soils. Understanding the fate of this carbon in the face global change depends on tracking the flow of electrons through the breathing of tiny microbes.