Secrets Of Spider Silk: New Study Uses Genome Sequencing To Examine Its Properties

May 11, 2017

Scientists are trying to unlock some of the secrets of spider silk by sequencing the genetic code of the spiders themselves. One new study is led by the University of Vermont and the University of Pennsylvania.

UVM biology professor Ingi Agnarsson, an expert on spiders and the properties of spider silk, is one of the researchers on that study.

"The goal of this study is trying to understand at the molecular level, the building blocks, how these materials are actually put together by the spiders to aid us in mimicking these properties in man-made materials," Agnarsson told Vermont Edition on Thursday.

Spider silk is one of the toughest materials in existence, with combined strength and elasticity that manufacturing techniques struggle to match.

"We're pretty good at making materials that are either very strong or maybe very stretchy," Agnarsson says. "But spider silk combine[s] the two, and it's in the combination of these two properties that makes them really, really tough."

Rather than just focus on the properties of the spider silk, this study actually sequenced the genome of a spider as a way to try and understand the silk better.

"A lot of the research that has been done on spider silk in the last 50 years has focused on the biomechanical properties, and we understand these pretty well," Agnarsson explains.

"So now the issue is: what is the structure of these materials that have this excellent performance? And that's where this study comes in, trying to understand the molecular makeup of these fibers whose biomechanics we have already characterized pretty well."

The spider whose genome was sequenced for this study is called a golden orb-weaver, which Agnarsson describes as "sort of the 'lab rat' of spider silk research, because they are easy to work with. They're very large spiders, so you get relatively thick fibers out of them. And they're easy to find in nature."

Agnarsson notes that golden orb-weavers don't live as far north as Vermont, but rather are common in the southern United States.

"Our first goal was simply to characterize the different types of silk they have and asking very basic questions. Like, how many types of silks do they actually make? How many types of proteins are each type of silk composed of? And what are the similarities and differences between different silk?" – UVM professor Ingi Agnarsson

Thanks to the genome work of the study, Agnarsson says the information they have collected and organized could be used to help address a number of questions about spider silk.

"Our first goal was simply to characterize the different types of silk they have and asking very basic questions," Agnarsson says. "Like, how many types of silks do they actually make? How many types of proteins are each type of silk composed of? And what are the similarities and differences between different silk?"

"So we've created this huge database, this resource, that we can now basically pinpoint the molecular structure of different types of silk, and start to answer these questions of, you know, what is it that makes this particular silk very strong or that other type of silk very stretchy? And so on."

There are actually different kinds of spider silk that serve different intended purposes. Agnarsson explains that some silk might be used for creating the web structure, another for coating a spider's egg sac and yet another to bind other fibers.

One finding that Agnarsson says was surprising had to do with the location of a certain silk protein within the spider's glands.

"The silk fibers come out of the end of the abdomen of the spider where all the silk glands are, and the venom is produced in the front of the spider – close to the mouth, obviously," Agnarsson says. "So there's no physical connection or proximity, but it turns out that one of the silk proteins is almost exclusively expressed in the venom glands."

While Agnarsson says they aren't sure why that happens to be the case, he does add that "silk strands themselves don't have any venomous properties as far as we know."

Agnarsson says he continues to be motivated by his personal curiosity and has a plan for building on this spider research.

"The next project is to take ... another species of spider that has a super strong, super tough silk, do the genome of that spider, and then compare the two and try to figure out what exactly is it that makes this new spider so different from other spiders," Agnarsson says.

Listen to the full conversation with Agnarsson above. Broadcast live on Thursday, May 11, 2017 during the noon hour; rebroadcast during the 7 p.m. hour.