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Gut Reactions:
How the contents of a termite’s stomach may revolutionize your car

Wednesday, April 12, 2006

One of the talents of great artists is knowing when to stop, recognizing the moment when a work has reached its maximum potential and having the self-control to put down tools and leave well enough alone. Termites would have brilliant careers, and gallery representation, if only they could acquire this skill. On a recent morning, I found myself admiring the work of a dozen termite colonies in a laboratory at Caltech, where each isopteral community had unconsciously sculpted a miniature wooden marvel. From half-inch slices of ponderosa pine, the infamous chewers had chiseled a series of luscious flowing forms, small layers of sculptural perfection that might have been the work of a pixie-scale Henry Moore. But of course termites don’t know how to stop, let alone when to, and the sensuous wooden slivers in the basement of the Keck Laboratory are doomed to be obliterated by the very artists that brought them into being.

These termite Michelangelos are the guests of Dr. Jared Leadbetter, an assistant professor of microbiology at Caltech’s department of environmental science and engineering. Not only is the work doomed, so are the artists. Leadbetter is interested in the contents of their stomachs, and each of these tiny creatures will eventually have its guts spilled across a microscope slide.
Leadbetter is an expert on the gut flora of termites, the colonies of microbes that live inside the insects’ stomachs and help them digest unpromising foodstuffs such as wood and grass. In the age of the Internet and the Hubble Space Telescope, this humble back-corner of zoology would hardly seem a promising place for high-tech investment. But then came the State of the Union speech, and ever since, Leadbetter’s phone has been ringing off the hook. “You tell people about this and their eyes glaze over,” he says with self-deprecating humor. “Then all of a sudden they hear about wood-chips-into-ethanol, and suddenly the venture capitalists are calling.”

Sadly, the venture capitalists are not interested in the science of termite -physiology; what they want is to get in on the ground floor of a fuel source that our president has been touting as an alternative to gasoline. As gas prices soar and the Middle East cooks, the race is on to develop new fuels, and among the chief contenders are hydrogen and ethanol.

Ethanol is already used as a gasoline additive, and some vehicles can run solely on that; Brazil now has a thriving ethanol car industry. At present automotive ethanol is distilled from corn or sugar cane, but people have dreamed of using wood chips, wood pulp and other wood waste as the feedstock. Waste wood is a huge untapped resource, and in his State of the Union address, the president suggested that it could one day be fueling the nation’s cars. In order to achieve that goal we need to develop viable industrial processes for making ethanol from wood; hence the interest in termites.

Termites’ penchant for wood is estimated to cost the Southern California economy a billion dollars a year. Homeowners across the Southland live in fear of infestation. “Fighting termites is like fighting gravity,” Leadbetter notes cheerfully. Sooner or later they are going to get you. “All it takes is for two alates [winged termites] to fly into your attic after a good rain and a new colony will begin to form. I tell people that everyone has termites.”

But termites’ reputation as monsters is unfair, Leadbetter says, a sentiment echoed on Web sites across the Net. Of the 2,600 species of termites globally, only a dozen do serious economic damage; the rest play a critical role in global ecology, breaking down fibrous cellulose and lignin, and recycling vast quantities of biomass. They can do this because of the unique communities of microbes living in their stomachs.

All animals, including humans, rely on symbiotic relationships with microbes in order to digest their food. Long overlooked, gut ecology is emerging now as a hot area of scientific research. At Stanford, David Relman has been making an inventory of the microbes that live in the human stomach — there is evidence that the specific mix of gut flora influences both the incidence of various diseases and how easily we put on weight.

Termites’ stomachs harbor around 100 different microbe species, many of them found nowhere else on Earth. They live there in the absence of oxygen, quietly performing a miracle of bio-molecular -transformation. How they metabolize something as tough as wood is still largely a mystery. Leadbetter sees himself as a kind of Columbus of the termite gut, an explorer in a new world documenting creatures that have never been seen before. In his lab at the Keck building, he offers to let me observe this world for myself. Since the microbes cannot survive long in the open air, he has to get us a nice, fresh termite gut, which means that one of the tiny artists has to be -sacrificed on the altar of science.

The disemboweling itself is gruesome but quick — the hardest part is picking up the wriggling insect with the tweezers. A rapid yank, and the intestinal tract is laid bare between the severed ends of the termite’s body, the gut itself a thin, reddish streak, which Leadbetter lays on a microscope slide.

Beneath the powerful eyepiece of the Axioplan microscope, Leadbetter cranks up magnification and invites me into his world. “It’s like being an ecotourist in Wonderland,” he says. And indeed it is. In the microscope’s circular view field is a teeming miscellany of exotic beasties, a little alien universe populated by creatures as strange and comical, and somehow as endearing, as one of those kitschy bazaar scenes in a Star Wars prequel. The most common type have a long, thin corkscrew form; these are spirochetes, closely related to the bacteria that cause syphilis. There are protozoans resembling miniature snails, and inside their single-cell bodies are small pieces of red stuff. That’s wood, Leadbetter tells me. My favorite type is the one that looks like a sea lion, which snuffles around with its “nose” twitching, apparently searching for something. The “sea lion,” whose Latin name is Trichonympha, has long cilia trailing from its body that helps it swim. All of these organisms propel themselves by chemotaxis, charting paths along chemical gradients in the water.

Leadbetter has been studying this microbial Serengeti for the past 16 years, but he is constantly seeing new species he has not yet identified. It’s a daunting task simply to catalog the different types, let alone to understand what each one does. “Why,” for instance, “are there 100 types of microbe, and not just one?” he asks.

These microbes are one of the major reasons termites are such legendarily social creatures. When a new termite hatches from its egg, it has no gut flora; it must be fed its microbial complement by another termite. Leadbetter is particularly taken by this fact — termites are alive today because millions of generations of termites before them have handed on their gut flora to the succeeding generation. It’s an insectoid version of the Catholic Church’s apostolic succession, in which each new priest is fed the communal wafer by his father-confessor. Termites have no theology, of course, but their survival as a species depends on this pan-generational passing of the torch.

Leadbetter and his colleagues are trying to understand what it is exactly the microbes do. They are beginning the process of making a cross-genome map of all the DNA collectively operating in the gut colony. Ideally, they would like to sequence each microbe separately. This kind of very basic biology is what we need to understand if we are ever going to work out how to efficiently turn wood into ethanol. As Leadbetter notes, “Making ethanol is not hard; making it from wood is the problem.”

I asked Leadbetter how long it might be before wood-to-ethanol is economically feasible. Clearly, it’s a question he’s heard before — not least from the venture -capitalists whose calls he usually ignores. “It all depends,” he answered, “on how much we are prepared to commit to doing the underlying science.” Unlike, say, particle physics, termite-gut ecology is complex stuff. It has taken nature a billion years to get to this point; it will take scientists at least a few decades to learn the ground rules. We ought not be priming the pumps just yet, Leadbetter suggests. But the end of oil is definitely nigh, and we must begin to look seriously for other fuel options. As prices climb at the pump, who knows, maybe this country will again get serious about supporting basic biological science.

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