Gut Reactions

The termite’s stomach, of all things, has become the focus of large-scale scientific investigations. Could the same properties that make the termite such a costly pest help us solve global warming?

Perhaps—but it won’t be easy. Last year, in an initiative that has been compared to the Manhattan Project, the Department of Energy founded three Bioenergy Research Centers, which collectively house scientists from seven government labs, 18 universities, and several private companies, and are aimed at making cellulosic ethanol competitive with gasoline within five years. The effort, which has $375million in funding, is focused on plumbing the structures of woods and grasses and learning how various creatures break them down; genetic modifications, scientists hope, could then enable us to make cheaper fuels. The centers are expected to come up with ideas that can be commercialized—actually making them more like Bell Labs, say, than like the Manhattan Project.

VIDEO: Author Lisa Margonelli captures footage from her termite-hunting expedition in the Arizona desert with researchers Falk Warnecke and Phil Hugenholtz

Started two years earlier, the termite proj­ect described in Nature is based on the same model of public and private collaboration, and is now an important part of the bioenergy initiative. Indeed, termites might be seen as an “indicator species” for the larger effort—and, as scientists are learning, they are full of devilish details and vexing complications.

In 2005, the microbial ecologist Falk Warnecke, of the Department of Energy’s Joint Genome Institute, traveled with researchers from Caltech and the San Diego biotech company Diversa to Costa Rica, where they opened up a termite nest in a tree. The group dissected 165 worker termites, freezing the contents of their third guts in liquid nitrogen and shipping them to Diversa’s lab. After extracting the DNA from the microbial cells, Diversa sent a sample to the institute to be sequenced.

Housed in a low brick building in Walnut Creek, California, the Joint Genome Institute is sequencing the genes of hundreds of plants and microbes that might be useful for energy production and environmental cleanup; it is a key part of the Bioenergy Research Centers. Originally formed as part of the Human Genome Project in the late 1990s, the institute has its roots in the Department of Energy’s decades-long interest in tracking genetic mutations in atomic-bomb survivors and nuclear workers. The scale of its current mission becomes evident as soon as you enter the lobby, where a TV screen displays a ticker that tallies sequences by the minute, day, month, and year. When I arrived at about 10 o’clock one morning last spring, the day’s total stood at 25,555,288 DNA base pairs, the twinned nucleotides that are the building blocks of genes. Every second, another thousand base pairs joined the tally. Employees call this incessant data stream the “fire hose.” The institute now sequences as much DNA in an hour as it did in all of 1998, and the pace is planned to double by the end of the year.

Even for people accustomed to avalanches of data, the effort to map the contents of the termite’s third gut is extraordinary. “A disgusting mess of a data set,” says Phil Hugenholtz, the head of the institute’s Microbial Ecology Program. An angular Australian in his 40s, he speaks in rapid bursts, like a human fire hose. Traditional genomic analysis sequences one organism at a time, but Hugenholtz is a leading practitioner of metagenomics—the new science of sequencing genes from whole environments of microbes at once, and sorting out the resulting jumble of loose DNA code with the aid of computer science, statistics, and biochemistry. Metagenomics is not only breathtakingly fast; it allows us to catalog genes that were previously unknowable because so few types of microorganisms—fewer than 1 percent of all species of bacteria—can be cultured in a lab. Many biologists regard metagenomics as a scientific revolution akin to the invention of the microscope. In practice, though, it’s a sloppy art.

When the sequencers finished, they had 71 million letters of DNA code in tiny fragments. They sorted the fragments, assembled them into longer chains of genes, and scanned the genes to determine their likely functions and which of the 300 microbes they might have come from. Scientists then looked for combinations of chemicals that might be enzymes, comparing the results to enzymes known to work on cellulose. The metagenomic picture of the termite’s third gut that has so far emerged is a portrait of codes and probabilities—more sophisticated than a photograph from an electron microscope, but less satisfying, because so much remains indefinite.

Next, the scientists set about the long process of figuring out how all the parts work. “It’s like trying to learn about a house when someone’s given you nothing but the blueprints—and they’re all ripped up,” Hugenholtz says. Still, the blueprints were stunning. The termite gut contained much more than enzymes involved in breaking down wood into sugars: for example, there were a hundred species of spirochetes closely related to syphilis but here devoted to, among other things, producing hydrogen. There were also 482 appearances of a mysterious giant protein that Warnecke says looks like the international space station. He drew me a picture of a long, Lego-like scaffold with different enzymes plugged into it, hypothesizing that the protein might help strip sugars out of wood. But that was only a guess: “One of the disadvantages of finding so much is that you don’t know what it all means,” he told me.

Hugenholtz and Warnecke began sifting through the questions raised by the metagenome. Why do termites have 300 microbes and 500 different genes to degrade cellulose? How do you go about deciding which microbe is the most important? Do some termite species have stronger guts than others? And what on Earth was the space station doing? To tackle these questions, they needed more termites. They took some from cow patties on a Texas farm, surprising the elderly landowners by asking for a signed waiver on whatever intellectual property might develop.

One afternoon I watched Warnecke dissect 50 of the new termites. He worked at a rapid clip, pulling the insects’ heads and anuses in opposite directions with a microscopically violent yank; each termite’s gut unwound into a short, lumpy string. He showed me an electron-micrograph image of the inside of the gut. It looked like an undulating carpet. On it were rod-shaped bacteria; Warnecke pointed out pimple-like structures on the sides of a few, which he thought might be the space-station-like giant proteins. He speculated that the proteins work something like a Swiss Army knife, holding an array of tool-like enzymes and catalysts outside the cell to grab pieces of wood and whittle away, allowing the cell to slurp up the sugars thus released. If this hypothesis is correct, the proteins could be a great fit for biofuel production, because those loose sugars could be fermented into ethanol.

But the magnified images were far from conclusive. Hugenholtz slumped in front of the screen and complained that he saw no wood in the gut—were the termites starving? He impatiently made a list of tests he wanted done. Hugenholtz is confident that the team will eventually figure out what the proteins do. “You really see the science flailing around blindly here—but then things crystallize out of the darkness,” he told me.

One morning when I met Hugenholtz and Warnecke at a coffee shop, they began to riff on how the gut might work. “You get the feeling the microorganisms are more dominant than the termite. They must have a way to control the insect,” Warnecke said. Hugenholtz interrupted, quoting a colleague: “Maybe the termite is just a fancy delivery system for the creatures in the gut.” We tend to assume that the larger organism in a symbiotic relationship is in charge, but relationships like the one between the termite and the microbes involve constant two-way chemical communications. Even human beings, Hugenholtz said, are subconsciously eavesdropping on chemical conversations between the inhabitants of our guts; this leads us to crave, say, potato chips when our microbes want salt. His eyes fell warily on his coffee. “Do you think our stomach bacteria have trained us?”

Presented by

Lisa Margonelli is an Irvine Fellow at the New America Foundation and the author of Oil on the Brain: Petroleum’s Long, Strange Trip to Your Tank (2007). More

Lisa Margonelli directs the New America Foundation's Energy Productivity Initiative, which works to promote energy efficiency as a way of ensuring energy security, greenhouse gas emissions reductions, and economic security for American families. She spent roughly four years and traveled 100,000 miles to report her book about the oil supply chain, Oil On the Brain: Petroleum's Long Strange Trip to Your Tank, which the American Library Association named one of the 25 Notable Books of 2007. She spent her childhood in Maine where, during the energy crisis of the 1970s, her family heated the house with wood hauled by a horse. Later, fortunately, they got a tractor. The experience instilled a strong appreciation for the convenience of fossil fuels.

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