They're spun thousands of times a second. They're so sinewy and commonplace, they hardly get noticed. And yet for decades, spider webs have stumped researchers.
No one has been able to create anything nearly as lightweight and flexible (not to mention waterproof) that is also many times as strong as steel. And visions of using spider's silk to make rip-proof clothing, from children's garments to military uniforms, have remained just that: visions.
But researchers are now closing in on understanding how spiders make silk, which may give them the key to creating a synthetic version. Spider's silk is one example of how advances in biotechnology and synthetic chemistry are fueling rapid growth in animal-based products. Nature is teaching scientists how to produce everything from better laundry detergent to rustproof paint.
In time, "biofactories" will create large quantities of cells and tissues to produce useful animal-based ingredients, predicts Murray Moo-Young, a chemical engineer at Canada's University of Waterloo.
Spiders are high on the research agenda because they produce several useful things, including one of the strongest materials in the world.
"If you've ever sort of pushed aside a spider web, you've noted that it pulls before it breaks," says Paula Hammond, a chemical engineering professor at the Massachusetts Institute of Technology. "Spider silk goes through this sort of stretching before it breaks, and in doing so, it absorbs a lot of energy. This energy-absorbing process is what makes the material so tough."
Spiders spin silk by secreting a fluid, fibrous protein similar to keratin, the same protein found in hair and horns. This protein hardens as it oozes, a process that scientists are only now beginning to understand. So far, they have been unable to produce fibers with the same strength.
But researchers at Tufts University near Boston have discovered how spiders and silkworms produce such strong fibers. Surprisingly, "the entire process is controlled by the amount of water," says David Kaplan, a biomedical engineer at Tufts.
By using the right balance of water, spiders and silkworms control the silkmaking process by preventing proteins from solidifying too quickly. Dr. Kaplan copied the process in the lab, giving scientists a new approach to making artificial silk and spawning hopes of an array of new products from body armor to clothing and superstrong rope.
Scientists are also turning to spiders in the hope of producing an ideal pesticide - one that can target and kill specific crop-destroying insects, while posing no threat to other insects, humans, or animals, says Glenn King, a researcher at the University of Connecticut. About the size of a small crab, Australia's funnel-web spider produces a venom made up of more than 100 compounds. Several of those compounds kill only specific insects, Dr. King says.
"By isolating these compounds from the spider venom and putting them in a common virus that affects only insects, the virus can deliver the toxin to a specific pest," he says. The result could be an environmentally safe pesticide - if scientists can figure out how to make the compounds in a chemical lab.
Another kind of venom - from snakes - may one day help out on laundry day. Chemist Devin Iimoto of California's Whittier College and his students have discovered that an enzyme extracted from the venom of the Florida cottonmouth (water moccasin) removes bloodstains from clothing.
Laundry detergents already incorporate enzymes made by bacteria. But using an enzyme produced by a larger animal is something new. The snake enzyme attacks bloodstains, breaking the attachments between the dried blood and cloth fibers.
Research is in its early stages and no companies are known to put snake-venom enzymes into detergents.
Other animals also are providing leads to new, more effective products. For example, mussels stick to objects such as rocks, cement pilings, and one another. Up close, it is easy to see the dozens of tiny filaments that stretch from their bodies and attach them to home turf. A mussel also has an organ called a "foot" that it extends, attaching each filament to a stationary object with a tiny dab of glue.
The foot repeats the process until it is secure enough to resist the pull of tides, currents, and predators. Purdue University researchers have discovered that the formation of mussel adhesive requires iron, a metal never before found in bioadhesives.
Most of these glues are based on proteins. When iron is added, the gelatin-like material hardens, says Purdue chemist Jonathan Wilker. Iron appears unique; the hardening does not occur in the presence of other metals that can be processed by plant and animal cells. This discovery could lead to improved adhesives, rustproof coatings, and antifouling paints to defeat barnacles.
Of course, making a product in the lab is far different from producing it on the factory floor. For example, before companies begin making detergents that remove blood by using snake enzymes, they have to get the venom. Snakes breed poorly in captivity and catching poisonous snakes in the wild to "milk" them for venom is difficult and dangerous. So scientists are developing laboratory cultures of cells that produce snake venom.
Spider silk will probably have to go the synthetic route. "You can't farm spiders the way you farm silkworms," Dr. Hammond says. "Spiders are very cannibalistic. If you put two spiders together in a cage or any kind of enclosure, eventually one spider will eat the other."
To create a synthetic fiber, Hammond's team starts with polyurethane, a common plastic used to make packaging and fabrics. So far, her team has made fiber that's both soft and stretchy. They are investigating the use of ultrasmall particles to make the fiber stronger.
Other researchers are trying to take a shortcut with biotechnology. A small start-up company in Quebec, Nexia Biotechnologies, is adding a silk-producing gene to New Zealand miniature goats. These animals produce from 2 to 15 grams of spider silk per liter of milk, vastly more than what a spider makes.
Nexia is raising two herds in Plattsburgh, N.Y., and St. Telesphore, Quebec. Eventually, the company wants to produce as much as five tons of spider silk a year.
• Wool: Central Asians began raising sheep for food and clothing about 10,000 years ago. In about 4000 BC, Mediterranean societies pioneered the spinning of wool into yarn.
• Leather: The tanning of hides dates to prehistoric times. Egyptian leather artifacts more than 3,000 years old have been found.
• Silk: China kept sole possession of silkmaking for more than 3,000 years; the technology spread after AD 550, when Byzantine Emperor Justinian I sent monks to China to smuggle out silkworm eggs and mulberry seeds.
• Parchment: In the 2nd century BC, paper made of skins was first used (instead of Egyptian-controlled papyrus) at Pergamum in Asia Minor to build the library of King Eumenes II.
• Whale oil: Basques began whaling in the 10th century, cooking down the blubber to make oil for lamps.
Sources: World Book; Encyclopedia Americana