Companies spend thousands developing a project for the market, hoping their investment will return big. Investing like this happens every day and won’t shock anyone. What may surprise you is someone who spends more than a decade and thousands of their own dollars to make an open-source version of a highly-marketable product. In this case, we’re talking about genetically modified yeast that produces spider silk. If that sounds like a lead-in to some Spiderman jokes and sci-fi references, you are correct on both accounts. [Justin Atkin] had some geneticist work under his belt when he started, so he planned to follow familiar procedures like extracting black widow DNA, isolating and copying the silk genes, and pasting them into a yeast strain. Easy peasy, right? Naturally, good science doesn’t happen overnight.
There are a few contenders for the strongest spider silk among which the golden silk orb-weaver gets the most attention, but the black widow’s webbing is nearly as strong, and [Justin] is happy to wear black widow inspired bling, whereas the golden orb-weaver looks like it crawled out of Starship Troopers. His first attempt to extract DNA starts with a vial of preserved
nightmare fuel spider specimens because that is a thing you can just go online and buy. Sadly, they were candied in alcohol, and that obliterates DNA, so he moved to dried specimens from breeders, which also failed to produce results, and those were just the landmark hangups.
After all the setbacks and dead ends, [Justin] and his lab crew take a different path and design a plasmid-to-order. Sheesh, you can buy anything on the Internet. Labs that build these sequences aren’t like a custom T-shirt producer because you can’t just send them Gattaca.TXT and a check. The labs will refuse sequences with repetitious snippets, and spider silk is long repeating chains. [Justin] has to make his recurrent silk look unique all the way through, and so he has to tweak nature’s recipe.
Silk is not a singular thing but rather a classification of what comes from a spinneret. Spiders produce as many as ten varieties of silk, and they are a combination of monomers. Some are sticky, some are stretchy, and some are strong, but for commercially viable stuff, we are interested in dragline which is firm and not elastic. It is safe to assume this is what [Peter Parker] loads into his web slingers. The variety comes from ordering and reordering the stretchy-strong sequence to increase the variabilty, but that only goes so far. [Justin] adds a new contribution to the mix, and that comes in the form of biomineralization, which we see in things like nacre (mother of pearl), chitin, and bones. This is one of the sturdiest things mother nature put into animals, so the improved formula has a little extra strength in the mix. Another ingredient is the sequence to tell the yeast to excrete the silk, not just produce it internally. This makes harvesting the difference between milking a cow and butchering one.
When the lab’s plasmid arrives, they mix it into some pichia pastoris yeast which is normally pinkish, but the modified strain is bone white. It is a fickle strain and doesn’t want to accept the new genes, but Youtube commentators provided helpful protocols. This in itself is an achievement, as if you can get the YT comment section to provide useful data, you deserve a trophy. After the new procedures, a battery of tests shows that gene modification took hold. [Justin]’s yeast was producing silk at a respectable rate. Wow.
Now, the plan is to find ways to do something with the mass-producible silk. We love the idea of growing tough-as-nails cargo pants or black widow web-shooters. Spider senses not included.
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