Potent methane microbe discovered in permafrost

Bacteria produce greenhouse gas even in frozen soil

Image of Hess Creek in Alaska, where researchers took soil samples to study microbial composition. © Courtesy of USGS Soil Carbon Research
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In the permafrost of the Arctic, researchers have discovered a previously unknown, methane-producing microbial species. This can produce the strong greenhouse gas even in frozen soil. When the soil thaws, the methane is released. "The frequency of this new methane bacterium indicates that it plays an important role in greenhouse gas production in permafrost, " the scientists report in the journal "Nature". With the help of gene analyzes they had investigated which bacteria are present in the permafrost and how the activity of these microbes changes during thawing.

"One gram of permafrost can contain thousands of different types of bacteria and billions of cells, " says lead author Rachel Mackelsprang of the Joint Genome Institute at Walnut Creek. But most of these microbes are still completely unknown. For the most part, it is impossible to isolate and breed them in laboratory cultures. Therefore, the reaction of these soil bacteria to the warming of their habitat is hardly explored.

Quick reaction to thawing

With the help of genetic analyzes of permafrost samples, they have not only discovered a new type of bacteria and have determined which metabolic processes take place in the frozen soil. "Our analysis also reveals, for the first time, the rapid and dynamic response of permafrost microbes to the thawing of their habitat, " say the researchers. Genes that played a role in the processing of nitrogen and carbon would have been particularly strong. For example, genes for nitrogen fixation decreased during thawing. This suggests that the permafrost may increase the greenhouse gas nitrous oxide when heated.

According to the researchers, this confirms that the response of soil bacteria influences the release of greenhouse gases from permafrost. Their behavior must therefore be further researched and included for forecasts of future development.

Permafrost stores enormous amounts of carbon

In large parts of the Arctic, the ground remains frozen throughout the year. This permafrost stores an estimated 1.67 billion tonnes of carbon in the form of various organic compounds. "This equates to the total amount of carbon presently present in all land plants and the atmosphere, " the scientists write. display

In the course of climate change, however, the temperatures in the Arctic continue to rise, the permafrost thaws. In it, bacteria decompose the organic compounds, releasing the greenhouse gas carbon dioxide.

Inventory of all genes in the soil

For the study, the researchers used the so-called metagenome analysis. It records the totality of all microbial genes and DNA building blocks in a sample without first isolating individual species. The scientists used it to study permafrost samples from Alaska, both frozen and thawed.

Nearly 40 billion different DNA building blocks have been found in the samples, the researchers report. From this one can conclude that the microbial community is extremely diverse in permafrost. However, metagenomics also reveals which biochemical pathways and processes take place in the soil, the scientists write.

"Using metagenomics, we can help to understand how the unexplored microbial species in permafrost process carbon and how much greenhouse gas they release in thawing, " says study leader Janet Jansson of the Lawrence Berkeley National Laboratory in California. This provides valuable information to improve the carbon cycle models and climate forecasts. (Nature, 2011; DOI: 10.1038 / nature10576)

(Nature / dapd, 07.11.2011 - NPO)