--FOR IMMEDIATE RELEASE—
September 1, 2011
CARBON IN THE DARK: A REVELATION FROM THE DEEP
WEST BOOTHBAY HARBOR, ME -- Researchers from Bigelow Laboratory for Ocean Sciences have discovered that many of the myriads of bacteria living in the deep ocean are able to use carbon dioxide to build their bodies in a process akin to plant photosynthesis -- but these bacteria convert carbon dioxide to organic compounds in complete darkness. Results of the new study by Swan, et al., have been published in the September 2, 2011 issue of the journal Science. (Brandon K. Swan, Manuel Martinez-Garcia, Christina M. Preston, Alexander Sczyrba, Tanja Woyke, Dominique Lamy, Thomas Reinthaler, Nicole J. Poulton, E. Dashiell P. Masland, Monica Lluesma Gomez, Michael E. Sieracki, Edward F. DeLong, Gerhard J. Herndl, and Ramunas Stepanauskas. Potential for Chemolithoautotrophy Among Ubiquitous Bacteria Lineages in the Dark Ocean. Science, vol 333, issue 6047, pp. 1296-1300.)
Funded by grants from the National Science Foundation, the Department of Energy, and other agencies, the discovery was made using a series of cutting-edge research techniques, including a combination of cultivation-independent single cell genomics and analyses of the physiology of individual cells. The project included collaborations with scientists from the U.S. Department of Energy Joint Genome Institute, the University of Vienna, the Massachusetts Institute of Technology, and the Monterey Bay Aquarium Research Institute.
“Photosynthesis is not the only way to produce biomass from carbon dioxide,” said Dr. Brandon Swan, a postdoctoral researcher at the Bigelow Laboratory. “Instead of relying on sunlight, some bacteria can harness chemical reactions to gain the energy needed for carbon fixation in the dark.”
This process, called chemolithoautotrophy, was previously thought to be limited to unusual environments in the ocean, such as hydrothermal vents. In contrast, the team’s research findings indicate that dark carbon fixation may also take place in deep, oxygenated water throughout the planet’s oceans, with the oxidation of reduced sulfur compounds, methane, and carbon monoxide likely replacing sunlight as energy sources.
“Our study suggests that previously unrecognized types of deep ocean bacteria play an important role in global biogeochemical cycles,” Swan added. “While photosynthesis is limited to the top 50-200 meters, the average depth of the ocean is a staggering 3.7 kilometers (2.3 miles), which means that these newly discovered microbial processes have a significant impact on the global carbon cycle.”
“This study is one of the first demonstrations of the power of high-throughput single cell genomics to decipher ecological roles of environmental microorganisms,” said Dr. Ramunas Stepanauskas, director of Bigelow Laboratory’s Single Cell Genomics Center and senior author of the Science paper. “Microbes drive most global biogeochemical processes, yet over 99% of them have resisted scientists’ attempts to grow them in cultures, rendering them inaccessible to studies using classical microbiology techniques. Culture-independent research tools, such as metagenomics, have provided initial insights into the gene composition of microbial communities, but have seldom been able to identify the specific organism to which a particular gene belongs. Single cell genomics bridges this gap, enabling the recovery of entire genomes from individual microbial cells without the need for cultivation.”
“This opens enormous new opportunities for studies of microbial ecology and evolution, and greatly facilitates the search for novel natural products and bioenergy sources,” Stepanauskas added.
“Our work indicates that autotrophic prokaryotes are likely much more abundant in the oxygenated water column of the deep ocean than hitherto assumed,” noted the University of Vienna’s Dr. Gerhard Herndl. “Also, it adds further support to the emerging notion that microbes are not randomly distributed in the deep waters, but rather are concentrated on particles, which are easily disrupted by conventional sampling.”
Dr. Tanja Woyke from the U.S. Department of Energy’s Joint Genome Institute considers the study to be a key step in examining the ecology of microbial communities in the natural environment.
“This very exciting study is the poster child for the use of single cell genomics to decipher functionalities of uncultured microbial consortia,” she said. “We expect this study to represent the beginning of an era of DOE-relevant science enabled by single cell technology.”
“It’s important to understand that the marine microbial world is vast and diverse, and by volume, the deep sea represents one of the most expansive habitats on our planet,” said Dr. Edward DeLong of the Massachusetts Institute of Technology. “Yet we are only now just beginning to learn the details of how these tiny microorganisms help balance the major cycles of matter and energy on our planet. New technologies such as single cell sequence analyses are helping to do that; however, fully integrated approaches incorporating physiology, biochemistry, biogeochemistry and systems ecology will all be critical for moving this field forward in the future.”