For want of a nail, the nursery rhyme goes, a kingdom was lost. A similar, seemingly innocuous changethe evolution of a lineage of mushroomsmay have had a massive impact on the carbon cycle, bringing an end to the 60-million year period during which coal deposits were formed.
Coal generated nearly half of the roughly four trillion kilowatt-hours of electricity consumed in the United States in 2010, according to the U.S. Energy Information Administration. This fuel is actually the fossilized remains of plants that lived from around 360 to 300 million years ago. An international team of scientists, including researchers at the U.S. Department of Energy Joint Genome Institute (DOE JGI), has proposed a new factor that may have contributed to the end of the Carboniferous periodnamed after the large stores of what became coal deposits. The evidence, presented online in the June 29 edition of the journal Science, suggests that the evolution of fungi capable of breaking down the polymer lignin, which helps keep plant cell walls rigid, may have played a key role in ending the development of coal deposits. With the arrival of the new fungi, dead plant matter could be completely broken down into its basic chemical components. Instead of accumulating as peat, which eventually was transformed into coal, the great bulk of plant biomass decayed and was released into the atmosphere as carbon dioxide.
"We're hoping this will get into the biology and geology textbooks," said Clark University biologist David Hibbett, senior author of the comprehensive study comparing the complete genomes of dozens of species of fungi, most of which were sequenced at the DOE JGI. "When you read about coal formation it's usually explained in terms of physical processes, and that the rate of coal deposition just crashed at the end of the Permo-Carboniferous. Why was that? There are various explanations. The evolution of white rot fungi could've been a factor perhaps a
|Contact: David Gilbert|
DOE/Joint Genome Institute