Montana State University

New bacterium found in microbial mats of Yellowstone

July 26, 2007 -- By Evelyn Boswell, MSU News Service

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BOZEMAN -- A heat-loving bacterium that reveals a new way to harvest light energy has been discovered in the colorful microbial mats around the hot springs of Yellowstone National Park. For only the third time in 100 years, scientists have found a new group of bacteria that turns sunlight into chemical energy.

"This organism provides insights into the history of photosynthesis and increases our knowledge of how solar energy is captured in this microbial community," said Dave Ward, a Montana State University professor who co-authored a scientific paper describing the bacterium. "Thus, this bacterium may have implications for alternative fuels."

The scientific paper will run Friday, July 27, in the journal, Science. The lead author, Don Bryant from The Pennsylvania State University, was a visiting scientist in MSU's Thermal Biology Institute during the summer of 2005. MSU co-authors are Ward, Christian Klatt and Mary Bateson; all in the Department of Land Resources and Environmental Sciences. Ward is also an adjunct professor in the Department of Microbiology.

Of the 25 major groups of bacteria in the world, only five were known to make chlorophyll and perform photosynthesis, Ward said. Then scientists found Candidatus Chloracidobacterium thermophilium in the microbial mats that reside in the outflows of Mushroom Spring and Octopus Spring, located about eight miles north of Old Faithful. The newly-found bacterium belongs to a group, called Acidobacteria. Ward said no one knew this group, which contains as much diversity as the plant kingdom does, included bacteria that could use light energy for growth.

In the course of conducting research sponsored by Ward's National Science Foundation award from its Frontiers in Integrative Biology Research Program, MSU scientists sampled the Mushroom mats in October 2003 and the Octopus mats in November 2004. The samples were used to generate large DNA databases, called metagenomes, which contain genes from organisms inhabiting the mat. Ward said Bryant discovered the first evidence of this unexpected and significant organism by analyzing these databases.

"I really wasn't skeptical at all because Don knows his stuff," Ward said.

"It's a very careful piece of science," Ward added. "Don is a very careful scientist. It's a blast doing science with someone like this, especially because he is excited about our interactions and is a pleasure to interact with."

The discovery of the new bacterium could have only come through genetic study because individual bacteria from the mat all look alike under a microscope, Ward said. He noted that, "It's like lots of people in the same disguise at the crime scene."

Bryant said in a press release from Penn State that, "Octopus and Mushroom Springs are intriguing to microbiologists because their unusual habitats are homes to a diversity of microorganisms, but many of them have proven difficult or impossible to grow as pure cultures in the lab. Metagenomics has given us a powerful new tool for finding these hidden organisms and exploring their physiology, metabolism and ecology."

Metagenomics allows scientists to study organisms without growing cultures in the laboratory. The researchers gather samples from the field, isolate DNA from the cells and go from there.

Ward said the microbial mats where the bacterium was found consist of layers and look like a slice of lasagna. The mats are found in springs emitting water that became alkaline by interacting with volcanic ash and lava flows inside Yellowstone's caldera. The mats look yellowish orange in the summer and greener in the winter.

The new bacterium grows near the surface of the microbial mats where the temperature ranges from 122 to 151 degrees. It competes for light with cyanobacteria (formerly called blue-green algae) and other bacteria, but contains so much chlorophyll that it thrives in that environment, Ward said. Each cell contains tens of millions of chlorophyll molecules.

The project was funded by the NSF, the Department of Energy, the NASA Exobiology Program and the Thermal Biology Institute. MSU is the lead institution on the NSF award. It also hosts Ward's NASA Exobiology Program grant and the Thermal Biology Institute grants that helped fund the project.

Evelyn Boswell, (406) 994-5135 or evelynb@montana.edu