How the contents of a termite’s stomach may revolutionize
By MARGARET WERTHEIM
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
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
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
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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