WHEN SILKWORM MET SPIDER
Scientists genetically engineer silkworms to spin spider silk and create a fiber that they hope will be stronger than steel
NOTRE DAME UNIVERSITY
Researchers added spider DNA to this silkworm so it can spin super-strong silk.
Scientists who meddle with the fabric of life are destined to meet an ugly fate. It’s a theme repeated again and again in novels and movies. Take Frankenstein or Jurassic Park.
So why would Notre Dame University researcher Malcolm Fraser create a caterpillar that’s part silkworm and part spider? Don’t worry, Fraser said he has no plans to create an army of giant spider-moths. What he wants to do is create a fiber that’s stronger than steel, yet lighter than the material that makes silkworms so valuable to the garment industry. “They’re not as strong as spider silk yet,” Fraser said. “We believe it’s a matter of a few tweaks and it will be as strong as spider silk, if not stronger.”
His work fits in a rapidly growing field of research called transgenics, in which genes from one organism are spliced into another’s DNA. It’s not exactly new. Farmers, for example, have for years used genetically altered corn and soybeans that tolerate glyphosate, an herbicide sold under the brand name Roundup.
At Ohio State University, researcher Kichoon Lee is splicing segments of DNA linked to human and animal muscle development into quail embryos. The plan is to identify gene-produced proteins that help the birds grow meatier after they hatch. Lee said the research could help farmers identify and breed chickens that are more likely to grow bigger. He said his work also could lead to methods to quickly heal muscle injuries in people.
But back to Fraser and his spider-worms. He said his research holds the promise of creating a fiber that could be used in lighter, more-durable clothing. Spider silk is five times stronger than steel. One species found in Madagascar can produce an “anchor line” that can extend more than 80 feet without breaking. Another type of spider produces silk that is almost as elastic as a rubber band, according to Randy Lewis, a University of Wyoming molecular biologist who has identified the proteins in spider silk and the genes that produce them.
Finding the right spider is half the battle. Spider silk cannot be mass-produced because, unlike silk worms, spiders don’t respond well to captivity. In fact, they eat one another. And Lewis said efforts to artificially assemble web proteins in the same combination created by a spider’s spinnerets haven’t worked. The idea to use a silkworm came from Kim Thompson, an entrepreneur based in Lansing, Mich., who created a company to develop and sell spider-silk-inspired fibers. Using Lewis’ research and advice, Fraser transferred the genes that make spider silk proteins into silkworm embryos. He also inserted genes that make bioluminescent proteins so that the hybrid worms and the spider proteins in their silk could be identified with ultraviolet light. When the light is shined on them, the silk grows green and the worms’ eyes glow red.
Using different genetic combinations, Fraser has created 20 strains of silkworm, each of which produces fibers that are a combination of silk and spider web. “They are basically a protein bioreactor,” he said. Fraser said more research must be done to analyze the molecular structure of these composite fibers. So far, he has been able to produce strands that are nearly twice as strong as silkworm silk. “We don’t know exactly what the proportions are between the spider silk and the silkworm silk,” Fraser said. The altered silkworms pass on their spider genes to their offspring, he said, eliminating the need to constantly create silkworms in the lab. Thompson said he hopes to sell the combined fibers to fabric-makers. Stronger fibers could help create lighter bullet-resistant vests and explosion-resistant walls and barriers. “We believe that we can make it stronger than spider silk, based on what we’ve learned so far,” Thompson said. “We don’t believe that what’s in nature is the limit at all.”
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NOTRE DAME UNIVERSITY The fibers produced by the mutated silkworm glow green because they include tagged proteins found in spider silk.
How to create a spider-silkworm
A team led by a Notre Dame University researcher has created a mutant silkworm that spins spider silk. How they did it:
- STEP 1 Scientists identify the genes in a spider that produce the complex proteins found in spider silk.
- STEP 2 The spider genes are placed inside a silkworm embryo using a process that uses a segment of parasitic DNA that inserts itself and the genetic material it carries into the DNA of the silkworm.
- STEP 3 Researchers examine the mutated silkworm for evidence that the spider DNA is now part of the organism. This is first revealed through genetic “tags” inserted into the silkworm DNA that produce proteins that glow in ultraviolet light.
- STEP 4 The silk is analyzed to determine how spider and silkworm proteins combine to create a ”hybrid” fiber. Researchers hope this could be used to make new athletic clothing, bulletproof vests and even airbags for cars. Source: Notre Dame University; University of Wyoming; KraigBiocraft Laboratories Inc.
