Mutant Worms Produce Piles of Spider Silk

Snippets of spider genes let mutant silkworms spin silk stronger than steel. Scientists have coaxed miles of spider-like silk from a colony of transgenic silkworms, opening the door for large-scale production of super-strong, tough and flexible fibers.

“We can make a lot more silk from the silkworm process than you could possibly make from spiders,” said molecular biologist Malcolm Fraser of the University of Notre Dame.

Spider silk has long been hailed as a superfiber, useful for everything from surgical sutures to bulletproof vests to scaffolding for growing cartilage. But spiders tend to be predatory loners who turn to cannibalism when raised in close quarters, making it nearly impossible to mass produce the treasured threads. A tapestry on display at the American Museum of Natural History last year took more than a million spiders to produce.

So scientists have tried to pull spider silk from tobacco plants, bacteria and even goats, with mixed success. Silkworms, on the other hand, are natural silk-spinning factories. A worm’s silk gland takes up about a third of its entire body, Fraser said, and a single cocoon can yield a thread up to a mile long. Silkworms have been domesticated for centuries and are already used for making mass quantities of marketable silk.

By inserting specific spider genes into silkworm chromosomes, Fraser and his colleagues grew a colony of caterpillars that produce threads nearly as strong as spider silk.

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