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Mashed-up genomes could produce biofuels

Using the genomes of 17 different ants, fungi and bacteria, scientists are sequencing the first-ever community genome, which could provide a source of biofuels.
Image: Leaf cutter ants
Leaf cutter ants carry leaves back to their colony. Using the genomes of 17 different ants, fungi and bacteria, scientists are sequencing the first-ever community genome, which could provide a source of biofuels.
/ Source: Discovery Channel

The genomes of 17 different ants, fungi and bacteria that eat through hundreds of pounds of leaf matter a year could ultimately lead to new techniques for making biofuels.

Scientists from the University of Wisconsin, the Joint Genome Institute and Emory University are sequencing the first-ever community genome, searching for clues to how what's essentially a 50 million-year-old bioreactor operates.

"These leaf cutter ants, fungi and bacteria can plow through over 400 kilograms [880 pounds] of dry leaves each year," said Garret Suen, a scientist at the University of Wisconsin at Madison who is working on the project.

"We believe that the whole community effort helps achieve this," Suen told Discovery News.

In the wild, armies of leaf cutter ants fan out across the rainforest floor searching for leaves. Using their powerful jaws, they cut out sections of leaves and then carry them back to their underground nests, where they feed the leaves to carefully tended gardens of fungi.

The fungi secrete enzymes onto the leaves that break down various molecules, leaving behind sugar that the ants use as food.

Once the fungi have broken down all they can, the ants remove the leaf pieces from the fungal garden, carry them to the surface and discard them in heaps around the nest. Bacteria continue to break down the leftover leaves, so the waste doesn't overwhelm the ant colony.

Exactly which molecules the fungi and the bacteria break down is still under investigation.

Only two other insect species have evolved such a close symbiotic relationship with fungi. Without the fungi, the ant colonies die. Without the ants, the fungi cannot survive. The bacteria are dependent on both for their food.

Over the last 50 million years, the three groups of organisms have optimized their relationship to squeeze the maximum amount of energy out of the leaves. How the community does this is still a mystery — one the scientists hope to unravel using a grant from Roche to sequence the genomes of all 17 organisms, including three different leaf cutter ant species.

Scientists estimate that there are roughly 1.5 billion base pairs spread out across the 17 different organisms. The human genome alone contains about 3 billion base pairs.

Locked inside the community genome could be clues that could eventually lead scientists to new enzymes or techniques that could enable humans to produce biofuels more efficiently.

"A systems approach is important for the biofuels field, because the breakdown of lignocellulosic with enzymes is still too expensive and cumbersome," said Lars Angenent, a scientist who studies how various microorganisms break down cellulose to produce biofuels at Cornell University.

"I think the work at Wisconsin should be applauded, because it does not sequence individual bacteria or insects, but rather the entire biological system," said Angenent.

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