The goats that make spider silk

In a farm in Wyoming, there a few unusual goats. From the outside, you would be unable to tell them apart from any other goats. But the Wyoming animals are special in that scientists can spin spider silk from their milk.

This may seem like a science fiction story, but it is not the product of anyone’s imagination. It is work made possible by the achievements of science and engineering, in particular by the development of technologies such as genetic engineering (genetic modification or GM, for UK readers) and its 2.0 version, synthetic biology.

Inside the DNA of every living organism, there is a set of rules that determines what the organism does and what it looks like. As biological research advanced, scientists learnt how to read and manipulate this genetic code and begun altering it by adding genetic information of an individual — typically associated to its useful features — into the code of another individual (not necessarily of the same species). Some bacteria, for example, have been genetically engineered for over 30 years to produce human insulin to treat diabetes.

Synthetic biology takes genetic engineering to another level. According to a 2008 briefing by the Parliamentary Office of Science and Technology in the UK, “established DNA research methods involve using genetic material from existing organisms,” while “synthetic biology is free of this constraint.” Some synthetic biologists use computers and laboratory chemicals to design and build biological parts, from a single gene to the entire genetic code, from scratch. Others, more closely related to established genetic engineers, re-design existing DNA building-blocks to give unnatural characteristics to existing organisms.

Dr Randy Lewis, the molecular biologist behind the silk-producing goats, is one of these re-designers who “puts pieces together” in ways natural biology could never do. His team began sequencing genes related to spider-silk production back in 1989. From studying this gene, they were able to understand better how spiders transform liquid proteins into strong silk fibres, and how the proteins’ structure is related to the incredible strength and elasticity of these fibres.

“We’re trying to alter both the strength and elasticity of the natural silks,” Lewis said in 2005 to National Geographic. “We’ve made a number of different synthetic genes based on what we found in natural silks — but altered in ways to make them even stronger and more flexible.”

To mass produce the custom-designed silk, the team needs an organism capable of making the right proteins. While they could simply bet on the natural silks and let spiders do the work themselves, these animals are, in Lewis’ words, “territorial and cannibalistic — you can’t really farm them in order to mass produce spider webs.” Goats, on the other hand, have been farmed for millennia.

Lewis — following up on work by Nexia Biotechnologies — had goats produce the silk proteins in their milk by adding the synthetic gene into their genetic code. The process is very tightly regulated so there are no harmful effects on the goats. Aside from those special proteins in their milk, the Wyoming animals are perfectly normal.

Transgenic baby 2.jpg

A transgenic baby “spider-goat” (photo: Holly Steinkraus/University of Wyoming, source: Popsci).

“When the goats have kids, and they start lactating, we collect the milk, and we can purify that spider silk protein in much, much higher quantities,” Lewis said to Science Nation, a US National Science Foundation publication. After filtering the proteins from the milk, they are exposed to the air to solidify and then wound onto a roller.

Because spiders have had 400 million years of evolution to perfect their weaving skills, and Lewis’ team is only starting, the custom-designed, goat-produced silks are not yet up to standard with their natural counterparts. But they are already stronger than steel and Kevlar — the material used in bulletproof vests — and have elasticities as great as rubber.

Once “spider-goat” silk is ready for mass production, the applications include artificial ligaments and tendons, strong sutures for surgery, and airbags. The US military, which is funding Lewis work, is interested in the silk for other uses such as light-weight bulletproof vests and parachute cables, as well as to repair bones of wounded soldiers.

Applications like these are typically what turns people’s attentions away from the possibly disconcerting fact that biologists are capable of giving goats an unnatural function. Similarly, the vast uses of the more extreme form of synthetic biologycreate a new organism from scratch — are what drives research in this area, despite ethical objections by some groups. From producing vast quantities of biofuel from renewable sources to creating cells capable of regenerating human tissue, the possibilities brought about by synthetic biology are endless.

This post was inspired by a promotional video on a forthcoming documentary on synthetic biology (which I found out about through Carl Zimmer’s blog). The film promises to explore the science behind this technology and its applications, and “it also raises questions about how life is defined, where ethical boundaries ought to be established, and how controllable or wild nature really is,” according to its producers. It should be interesting!

On another note, this was my first post on molecular biology, an area I’m unfamiliar with. If you have any comments, corrections or suggestions to the text, I would be happy to hear from you. Use the comments box below or write to dinnerpartyscience[at]


6 thoughts on “The goats that make spider silk

  1. Laura Wheeler

    Thank you Barbara for this intriguing post I would never have thought you were unfamiliar with the subject.  I personally find synthetic biology a fascinating field of science. 
    Synthetic biology has such great potential and for those who are unaware of the field’s capability, it is both scary and wonderful.  These transgenic goats are producing something that is useful and functional, making a process that is ordinarily time consuming and expensive more efficient.  Synthetic biology has the ability to aid cheaper synthesis of not just spider’s milk, but pharmaceuticals and energy, it can allow us to achieve a better understanding of life process, the environment, and even provide us with security against bioterrorism.
    I once worked on a science documentary where we briefly covered a great example of applied synthetic biology. We researched a place called LS9 in the US who were manipulating bacterial DNA (e-coli) to produce diesel.  They were harvesting this ‘bacterial made’ oil from the cells and it could be administered straight in an engine.  This “one-step” fermentation process eliminates the need for any additional chemicals and the industrial processes- ultimately saving time, money and energy
    However as you mentioned there are many associated moral dilemmas.  Synthetic biology is the re-design of existing biological systems or the fabrication of biological components and systems that do not already exist in the natural world.  There are many groups and individuals who believe that altering the natural world is wrong, and this does not necessarily always come from religious perspectives. People are apprehensive as they feel that engineering nature for our own benefit could have consequences we can’t anticipate- or don’t understand.
    Synthetic biology I guess has the ability to speed up evolution; only time will tell what the future holds.  Does anyone else have any interesting examples of synthetic biology? 


  2. Barbara Ferreira

    Thanks for your very informative comment Laura! As you probably know, some of the issues people have raised with synthetic biology are similar to those of its 1.0 version — the old GM. There are scientists in fields such as ecology who are concerned about the possible impacts of GM organisms in the ecosystem. For example, if you genetically modify a crop to be resistant to a certain disease, then you might be helping the organism responsible for that disorder to evolve to be able to attack the GM plant. (A bit like antibiotics and multi-resistant bacteria.) So far, there is no cause for concern but who knows what the future will bring? 
    I think there should be a lot more public understanding and debate about the pros and cons of synthetic biology. But one thing is certain — with the first synthetic cell already here — we should learn to stop worrying and love synthetic life.


  3. Laura Wheeler

    I guess the fear is that synthetic research, particularly the work carried out by Craig Venter and his team, the real leaders in the field, could be abused.  The fear is that this research could result in millions of people being wiped out by a plague like in the Will Smith film I Am Legend.
    I do think this is unrealistic, but GM crops have not always produced great results. More than 80 percent of the corn, soy and cotton grown in the US has been engineered with bacterial genes to resist insect pests or the herbicide, known as glyphosate.  Since the introduction of glyphosate-resistant crops, up to nine important weed species, like giant ragweed and pigweed, have independently evolved resistance to the weedkiller. This resistance was not spread by the crops’ pollen, but rather through strong selection pressure caused by the nearly indiscriminate use of the herbicide.   This new strain of ragweed is so resistant that it can take over farmers’ fields, wreaking havoc on the harvesting of crops and their livelihoods.  This is just one example of the negative results of genetic modification. 
    Generally there is not a lot of public trust in genetically modifying anything and as a result I guess people worry if Craig and his team have already successfully created man-made, replicating bacterial cells, what would happen if they accidently produced bacteria that’s resistant to antibiotics…..or if they were able to produce an agent that was harmful to humans.  Furthermore if the technology that they are perfecting got into the wrong hands, it could be used to create biological weapons.
    However I must make it clear I am all for synthetic biology research- I love synthetic life- as long as there are boundaries and rules in place to make sure everything is safe! What do other people think about it? 


  4. Laura Wheeler

    @Nicolas I loved Homer’s spider pig, and how he ended up neglecting Bart for it!
    We can laugh about it but I don’t see why things like this are not possible in the future, the potential for synthetic biology is endless….It also reminds me of an episode of the Big Bang Theory when Sheldon loses his job and decides to carry out science experiments in his apartment- he ends up creating glow-in-the-dark fish. The real life versions can be seen here, I want some glowing fish!
    Any one else have any other cool examples of genetic modification or applications of synthetic biology?


  5. Barbara Ferreira

    @Nicolas: oh Homer, I love that clip! In all seriousness, they used goats because they can be domesticated and because drugs produced in goats’ milk had previously been FDA approved (sorry, I don’t have a link for this one but the guy talks about it in the synthetic bio clip). More recently, the same people managed to get silkworms to produce spider silk, which is less "freaky", I suppose, although equally fascinating!
    @Laura: you should read this really interesting article about the hype around synthetic biology — because of its endless applications — and about how it’s time for the field to deliver. It includes examples of possible future applications of synthetic biology and of what has already been done.


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