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The Hidden Power of Plants

HAVING SPENT HIS CAREER studying a type of leaf-cutting ant native to the rainforests of Costa Rica, Cameron Currie never imagined he’d have much to offer on the subject of America’s insatiable thirst for gasoline. A native of the Canadian prairie with an abiding curiosity about evolutionary biology, Currie came to CALS in 2004 as an assistant professor of bacteriology with his ants in tow. These days he is caretaker to some 50 nests of the insects in his laboratory, where he studies their symbiotic relationships with fungi and bacteria. Fascinating and enlightening work, yes––but hardly connected to the problems of gas-guzzling SUVs and spiraling oil prices.

Except that maybe it is. Currie’s ants, belonging to the genus Atta, do something remarkable, a capacity shared only by humans and a few other insects. They grow their own food, tending vast gardens of leaves that provide nutrients for the main source of the ants’ diet, a strain of fungi related to common mushrooms. And while humans began farming around 10,000 years ago, these ants have been at it for some 50 million years. Is it possible––especially as we enter the dawn of a new era of agriculture, in which we hope to cultivate crops that we can easily convert into energy sources––that the ants in Currie’s lab could teach us a trick or two?

That possibility intrigues Tim Donohue, scientific director of UW-Madison’s newly minted Great Lakes Bioenergy Research Center. Launched by the largest federal research grant ever received by CALS, a five-year, $125 million award from the U.S. Department of Energy, the center has lassoed a diverse group of researchers to come up with new ways of drawing energy from non-food sources, such as plant stalks, wood chips, crop residues and agricultural waste. The idea of turning the planet’s organic leftovers, collectively called biomass, into energy has great appeal as an alternative to fossil fuels, but the methods for making fuel from plant biomass aren’t yet anything close to a commercial reality, a bottleneck Donohue and the center hope to overcome.

In the last 100 years or so, we have gone through a very significant fraction of fuels that it has taken this planet millions of years to accumulate…This is an experiment we only get to do once.

And that’s where ants come in. As opposed to corn kernels, which are made up of simple sugars like glucose, plant stalks and leaves are comprised mainly of cellulose, a tough polymer that gives plants structure. One of the most common organic materials on the planet, cellulose is a polysaccharide, a long chain of linked sugar molecules that must be broken apart before the sugars can be processed. The reason we can’t eat tree branches, for instance, is because our bodies lack the digestive enzymes to attack the chemical bonds in cellulose and get at its sugars. The same problem exists in the ethanol process; we don’t have efficient means for degrading cellulose into soluble materials that can be fermented into alcohol-based fuels.

But Currie’s ants may. Their nests harbor an array of microbes, most of which are unknown to science, and

Currie believes many of those microbes play essential roles as leaves are broken down and cycled through the ants’ gardens. Given that this collaboration has been perfected over millions of years of evolution, it’s not unreasonable to expect that we might find something useful––a microbe particularly adept at degrading cellulose, for example––in those nests if we looked.

The thing is, no one has thought to look, not until Donohue struck up a conversation with Currie about his new bioenergy center.

“It’s not an obvious connection,” says Currie. “But there is enormous potential to learn how these ants are using microbes to break down plant material, and those discoveries could be highly relevant to bioenergy.”

ANTS may never solve the world’s energy problems, but it says something that they’re getting a chance. Certainly, it speaks to the growing urgency surrounding the search for alternatives to fossil fuels, which provide more than 85 percent of the human-generated energy on the planet. With supplies of crude oil dwindling and worldwide energy demands projected to rise by more than 50 percent in the next two decades, it’s hard to make the math add up to anything less than a crisis.