Termites' Guts Could Yield Alternative Fuel Source

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http://www.eastbayexpress.com/Issues/2005-09-07/news/feature.html

Bug Juice

Could termite guts hold the key to the world's energy problems? Don't laugh.

Here are a few numbers to keep in mind regarding the future of hydrogen-powered cars:

Tailpipe emissions: zero.

Dependency on foreign oil: zero.

Number of termites crawling the planet: One hundred quadrillion. That's a one followed by seventeen zeros.

Granted, not many people are hip to the termite part of the equation yet. And most of those who are can be found in Walnut Creek working at the Joint Genome Institute, a branch of the federal Department of Energy that is looking for alternative fuel sources in some very unexpected places -- like a termite's gut.

Even groups as disparate as environmentalists and auto industry execs can agree that hydrogen is a promising alternative to gasoline. Engines powered by the stuff are twice as efficient as their gas or diesel counterparts, and emit only distilled water -- which means no smog, no refineries, no $3-a-gallon gas. The public is hungry for clean vehicles, most auto manufacturers are developing prototype fuel-cell cars, and California recently ponied up $54 million to build hydrogen fueling stations statewide.

So what's the holdup? Sure, there are still significant technology issues, and fuel-cell vehicles are years from commercial viability, but perhaps the most profound problem lies on the supply side: Nobody knows where all this fuel is going to come from.

You can't just tap into a pre-existing supply of hydrogen the way you drill for oil. It has to be manufactured, which is typically done by stripping hydrogen molecules from water or natural gas using electricity. But hydrogen produced this way is only as environment-friendly as the electricity source used to make it. So-called "brown" hydrogen is indirectly derived from the big three -- coal, oil, and natural gas -- with greenhouse gases and other pollutants as byproducts, while "green" hydrogen requires electricity from sources such as wind and solar, which are renewable but represent a minuscule fraction of US electricity production. For years, energy experts have been searching for the holy grail: a way to make hydrogen that is cheap, nonpolluting, and scalable to the mass market.

Philip Hugenholtz, head of the microbial ecology program at the Joint Genome Institute, thinks nature may have the answer. Many microbes make hydrogen, after all, sometimes in vast quantities. His team believes the most promising candidates are bacteria that live in a termite's gut, quietly breaking down plant matter and releasing hydrogen as a byproduct. These microbes make termites the most efficient hydrogen producers on the planet: From a single sheet of printer paper, a termite can produce two liters of the valuable gas. "We don't know how they do it, but we know they do it well," Hugenholtz muses.

And there's the rub -- until recently these bugs within a bug have received scant attention from scientists. We know the bacteria are a motley crew consisting of at least six different lineages more distantly related to each other than human beings are to trees, but little is known about how they operate. Of at least 200 different microbial species living in the termite's nether regions, 190 are pretty much terra incognita. Indeed, when the JGI team sequenced microbial DNA from the first test batch of termites they found in Costa Rica, they were elated to discover as-yet-uncharacterized species of bacteria.

The trick is to figure out which bacteria make hydrogen, and which enzymes they use to do it. With this information, Hugenholtz says, you could replicate those enzymes in mass quantities to produce hydrogen on a commercial scale. What's more, you could fuel the process with agricultural and industrial waste -- lumber-mill tailings, scrap cardboard, and the endless tons of corn husks and sugarcane stalks that are burned or discarded because they're too tough for farm animals to eat. "It's kind of recycling, making use of what's already there," says Falk Warnecke, a JGI microbiologist working on the project.

This line of inquiry excites energy experts who think we'd be better off farming our energy resources than drilling for them. "It's going to be in the long run a dirt-cheap way to make hydrogen in a very easy-to-do manner," says physicist Daniel Kammen, director of the Renewable and Appropriate Energy Laboratory at UC Berkeley. "I think that's exactly where hydrogen could and should come from."

It's too early to tell, but you can't beat the irony that one of our planet's most reviled species could be key to cleaning it up.

Jared Leadbetter didn't get into the termite business to save the world. The fact is, he just really, really likes termites. An assistant professor of environmental microbiology at the California Institute of Technology, Leadbetter first proposed the project to the Joint Genome Institute, and now serves as its lead investigator. He has been studying the inner workings of termites for fifteen years, sucked in, he says, by the complexity of a wild kingdom so tiny it fits inside a drop of fluid. "The termite hindgut is filled wall-to-wall with these fascinating morphologies of organisms," he explains. "I was really gripped with it in the same way you might be interested in going through a rainforest -- you don't have to be a scientist to appreciate that this is a beautiful place."

Termites owe their survival to their exotic profusion of gut inhabitants. The symbiotic relationship between insect and bacteria has been fine-tuned by millions of years of evolution to make termites and their tenants utterly codependent. Air is poison to these microbes, so living in the gut keeps them safe. The termite also chews wood into tiny pieces its guests can manage. In return, the bacteria digest the termite's food into something it can use. Without them, the insect would starve.

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Wood and woody plants are rich in long, complicated polymers called lignocellulose, the stuff that gives trees structural rigidity. But most animals, including termites, can't extract energy from this roughage. Ruminants like cows and sheep can handle grass, but, as Leadbetter points out, "Grass is like butter compared to wood." The termites' tenants most likely tackle the tough stuff as a team: First, bacteria called fermenters break the polymers into simple sugars, releasing hydrogen into the gut as a byproduct. Other bacteria use the hydrogen and sugars to make acetate, basically vinegar, which the termite can process as food. The ultimate byproduct is the greenhouse gas, methane; these termite-gut bioreactors produce an astounding 4 percent of the planet's atmospheric methane.

The insects aren't born with the microbes -- they are fed the bacteria by other members of their colony, and must be re-fed every time they molt. It's a sort of eternal flame that has been passed by one termite generation to the next since the insects first appeared in the fossil record more than a hundred million years ago. "Termites are one of the truly social animals like ants or bees or ourselves, and it's believed that one of the underlying reasons for why they're social is to maintain their microbiota," Leadbetter says. "They can't live alone."

This partnership has clearly succeeded: Termites are one of the planet's most abundant animals. There are more than 2,500 species, each adapted to eating whatever plant material is at hand. To sample some of them, Leadbetter and his fellow scientists traveled to Costa Rica this past summer. They hacked chunks of termite nests from trees and trucked the live bugs in their nests back to a local lab. The termites were iced to slow down their metabolism, and then individually dissected to recover the fluid from their guts -- hundreds were needed to fill up even a tiny vial. The researchers then extracted DNA from the microbes and sent it to the Walnut Creek lab for sequencing. By scouring the sequences for genes that encode known bacterial structures -- a flagellum here, a protein pump there -- they can get a better idea of how each microbe is built and which chemical pathways it uses to eat its lunch. The group plans to visit a half-dozen other sites around the world in search of termites that live on different types of plant materials, and, ultimately, the specialized microbes that allow them to do so.

Best-case scenario: The scientists identify a single microbe with a single gene encoding a single enzyme that is responsible for producing hydrogen. "If breaking down the lignocellulose is mediated by just one pathway or just a few enzymes, then that becomes something that may be able to be made easily into an industrial process," Hugenholtz says. "However, if it turns out that there are fifty different organisms each contributing fifty different enzymes to the process, then it's going to be much more difficult." But nature seldom takes the simplest path. Leadbetter and Hugenholtz agree that a more complex situation is far more likely -- after all, Leadbetter notes, if only one or two of those two hundred species were doing something useful for the termite, evolution would have booted the freeloaders millions of years ago.

Assuming they can identify the right microbes or enzymes, how would the scientists proceed? There are several approaches. They could build a bioreactor to simulate termite-gut conditions and use it to grow mass quantities of the bacteria, feeding in agricultural wastes and harvesting sugars and/or hydrogen. Or they could pinpoint the genes essential to hydrogen production and splice them into a microbe like E. coli or the yeast Pichia, which are easy to grow on an industrial scale. These host microbes would serve as factories for the desired enzymes, which a hydrogen producer could then use to break down plant matter directly. This is becoming a standard technique -- most of America's insulin supply, for instance, is produced this way. Diversa Corporation, the project's private partner, already uses similar strategies to manufacture nearly a dozen enzymes for agricultural or pharmaceutical use.

However it's accomplished, the result would be the same: a new economy of scale in production that could make hydrogen a more serious contender in the global energy marketplace.

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