SCIENCE : Enlisting Microbes to Do a Spider’s Work : Scientists clone arachnids’ genes, inserting them into bacteria to produce the insects’ strong, resilient thread.

LARAMIE, Wyo. — As spinners of silken thread, spiders far outclass the lowly silkworm and its cousins at producing the finest, toughest and most elastic fibers in nature.

And unlike silkworms, which spin a cocoon once in a lifetime, spiders can replicate their webs again and again. So why aren’t the threads of spiders as commonplace as those of the silkworm? Because these most territorial of creatures need space to weave their magic, a “spider ranch” would have to be so vast as to be economically prohibitive.

Enter molecular biologist Randolph V. Lewis, who has found a way to make microbes do the work of arachnids--and do it on a scale that, in theory, could lead to surprising applications, from superfine elastic sutures to cables strong enough to catch jets on aircraft carriers.

Lewis and his research team at the University of Wyoming have cloned four of the genes that spiders use to weave their webs. Inserted into the DNA of E. coli bacteria, these synthetic genes direct the microorganisms to produce the same protein building blocks found in arachnid silk.

So far, the researchers have harvested only about 10 milligrams of the protein globules.

“We’d need to make about 100 times that much before we can start making large amounts of fiber for testing,” says Lewis, a 44-year-old Wyoming native whose laboratory is only one of two in the world known to be studying spider silk. “But it’s very reasonable to think that we could have fiber in large-scale production within five years.”

For centuries, people have been intrigued by the glistening symmetry of spider webs and their unique properties. Webs were gathered in some societies as a poultice because they were thought to encourage blood clotting. During World War II, spider silks, which range from one-fifth to one-tenth the diameter of a human hair, made durable cross-hairs for bomber sights.

As recently as the 1950s, researchers discovered that some spider silk is nearly as strong as steel, able to withstand the weight of 300,000 pounds per square inch and bounce back to virtually its original length. And webs won’t dissolve in most liquids.

The potential for defense and commercial products was obvious, but no one could overcome basic production problems: The females that spin the webs must be caged or they would attack each other. Lewis suggested another approach entirely.

“Our pitch was to do it at the cloning level,” the researcher says.

Armed with a grant from the Office of Naval Research, Lewis in 1988 began exploring the chemical bonds of spider silk with Wyoming cat-faced spiders and the longer-lived golden orb weavers, subtropical arachnids found from Florida to Central America that can spew golden threads up to 100 yards long.

The golden orb weaver secretes more than half a dozen types of silk in weaving its web. Lewis and his team replicated four genes that make proteins found in two types of silk, including “dragline,” the major thread used by spiders for strength and elasticity.

The next step was to infuse the cloned spider genes in E. coli, a common microbe that is used to produce proteins such as the human growth hormone.

Once they got E. coli reproducing spider proteins, the researchers froze the bacteria, then thawed them so that their cell walls would break, releasing the material in tiny amounts that are later purified into small crystals.

David Kaplan, who heads a team in the biotechnology division of the Army’s research and development center in Natick, Mass., that is in “friendly competition” with Lewis, says both groups are trying to learn exactly how spiders take water-soluble proteins and excrete them as insoluble silks.

“The question is, can we even duplicate the kinds of fibers a spider makes,” says Kaplan, whose research is exclusively on the golden orb weavers’ dragline silk. “We really don’t even know how the spider makes it.”

The Wyoming team has yet to glean enough material to produce actual silk. But, Lewis says as one of his palm-size female spiders crawls up his sleeve, “we think we know how to do it.”

That will take more research dollars, and the molecular biologist is making the rounds, applying for a variety of grants to continue the work.

Still, Lewis envisions a day when he will see vats of E. coli several stories high producing pounds of silk.

No one is likely to be wearing robes of spider silk any time soon. Its remarkable properties are more likely to be used, Lewis says, by the medical community for sutures one-tenth the size now available, perhaps for artificial ligaments, tendons and reinforcements for human joints, and perhaps even for super-strong yet lightweight coatings for the defense or aerospace industries.

For Lewis, the real kick comes in trying to understand at the most basic chemical level how a spider makes such superior materials.

In that regard, he’s something of a pioneer, says Maurille Fournier, professor of biochemistry and molecular biology at the University of Massachusetts at Amherst. “Randy is a biochemist who recognized very early in his career, before most researchers, that nature has lessons to teach us.”