On a small farm, nestled deep in Northern Utah, something extraordinary is happening: creatures are being bred that are part goat, part spider. Last week’s episode of the BBC’s epic science series Horizon followed Adam Rutherford as he journeyed to meet these fascinating hybrids and their creator to find out more.
In charge of the unusual herd is Randy Lewis, a professor of genetics at Utah State University. The farm is a university outpost where they research modern farming techniques, teach animal husbandry and raise the intriguing “spider-goats”.
Since the first genetically engineered bacteria in 1973, we have been able to exploit the universality of the DNA code by cutting and pasting bits of DNA from one species into another. More recently, this editing technology has progressed and expanded into the field known as synthetic biology, and DNA code is effectively interchangeable between all species.
Using synthetic biology techniques, Randy and his team have taken the gene that encodes dragline silk from an orb-weaver spider and spliced it into DNA coding for milk production in the goat udders. This new genetic sequence was then inserted into an egg and implanted into a mother goat.
Now when their beloved spider-goats, Freckles, Pudding, Sweetie and the gang, lactate their milk is full of spider-silk protein – they produce “silk-milk”.
The milk is then processed to extract the spider protein and run around a spool to be collected. This process is considered extremely exciting because naturally occurring spider silk is widely recognised as the strongest, toughest fibre known to man. Its tensile strength is greater than steel yet it is 25 percent lighter than synthetic, petroleum-based polymers.
“We’re interested in dragline silk – the silk that spiders catch themselves with when they fall. It’s stronger than Kevlar. It really has some amazing properties for any kind of a fibre,” Randy explained.
It could be argued that breeding spider-goats is merely an extension of our 10,000 year old farming practices. All livestock and arable products have been genetically selected. They are carefully bred to produce the most desirable characteristics with each cross being a genetic experiment of its own.
“The trouble is, you can’t farm spiders,” Randy mused. “They’re very cannibalistic.”
The impressive and desirable properties of spider silk means Randy’s apparently bizarre research is extensively funded. Studies have shown that the silk is not only incredibly strong by is also compatible with the human body. So far, no inflammation or negative reaction has been found when the silk has been inserted into the body. It’s already known that silk good enough to be used in ligament repair can be made and it is hoped that, within a couple of years, tests to determine the best designs and the best materials that can be produced, will be underway.
This could include creating strong, tough artificial tendons, ligaments and limbs; repairing other tissues; healing wounds; or creating super-thin, biodegradable sutures for eye or neurosurgery.
As amazing as it is, this extraordinary piece of bioengineering isn’t even on the cutting edge anymore. The fast moving field of Synthetic Biology now incorporates an extensive variety of genetic exploration techniques; and personally, I can’t wait to see what they come up with next.
Horizon: Playing God presented by Adam Rutherford is available on BBC iPlayer