A New Flavor of Goat’s Milk Is Laced with Spider DNA

Soft, creamy chevre, spread on a nice cracker. Smooth, tangy yogurt drizzled with fragrant honey. Mexican cajeta, or thick caramel, dark, rich and bittersweet: goat's milk brings its rich, high-fat deliciousness to all three. And now, scientists at a university in Utah are spinning up a new variety of this favorite dairy product, one loaded with the silk of the golden orb-weaver spider, a huge, gnarly arachnid that caused something of an internet sensation in 2008 when an Australian photo circulated showing a particularly giant specimen devouring a bird about three times its size. But wait, it gets even freakier: The scientists get the silk into the milk via genetic engineering, splicing spider genes into goat embryos and then implanting them into the uteruses of unsuspecting goat does. When those little spider-goats grow up and begin producing milk, it's loaded with the golden orb-weaver's silk.

You don't have to worry about getting a mouthful of spider web the next time you take a cool draught of goat milk though. The Utah State University program isn't producing the milk for consumption, but rather as way to manufacture the spiders' silk for eventual use in a range of commercial products, from parachute fabric to bicycle tires to climbing ropes and, most promisingly, artificial ligaments and tendons, which don't yet exist and have the potential to revolutionize medicine. Wait, what?

"The medical applications have very interesting possibilities," said Randy Lewis, director of the synthetic silk program at USU. "Any of them would be a goal at this stage."

All spider silk is five times as strong as steel of the same diameter, and is also waterproof and elastic. But as Lewis explained, the silk of the golden orb weaver—besides being pale gold in color, hence the name—is even stronger than most species, capable of ensnaring snakes and birds, as linked to above. That makes it an excellent fiber for a range of applications, both within the human body and without.

But harvesting the silk directly from the spiders isn't possible. Besides being rare and difficult to work with, golden orb spiders are also cannibalistic. Goats, Lewis said, are perfect lab animals, because they require far less feed than do, say, cows to produce the same amount of milk, and are also smaller and easier to work with.

"And baby goats are just much cuter than baby cows," he said.

Not that manufacturing the silk in goats is an easy task. Using technology developed by Canadian biotech firm Nexia in 2000, the team at USU first isolated the spider gene responsible for silk production. Then, they splice that gene into E. coli bacteria, which are lab-friendly and multiply like crazy, to grow tons more of it. Next, the scientists select a goat cell from a skin tissue sample, cut out its nucleus, and nestle the modified spider gene in right next to the cell's milk-producing genes. After adjusting lab conditions so that the egg is convinced it's fertilized, Lewis said, the embryo is implanted into a goat doe's uterus.

"one hundred and fifty days later, you have a kid," Lewis said.

Right now, USU's herd consists of about 42 does and six new kids, with another round scheduled to be birthed this week. The transgenic goats look and act just like normal goats; the only way to tell whether a kid carries the spider gene is to test its DNA.

Things get complicated again when the grown-up transgenic goats are milked and it's time to strain out the spider silk protein. Essentially, the team at USU passes the milk through a series of filters with smaller and smaller holes, first separating the milk's liquid from its fat and then isolating its natural proteins from the silk proteins that the spider DNA brings to the party. As if the whole process weren't already bad-ass enough, that protein is then freeze-dried, creating a product that Lewis coyly described as looking like "um, you know, a little packet of white powder."

So far, the silk protein created at USU doesn't have any commercial applications, but Lewis foresees the non-medical products hitting the market in about two years; things like tendons and ligaments will take longer, he said, due to the need for FDA testing and approval. It'll be a while before we see the first real Spider Man; for now, we'll have to settle for spider bikes instead.