Recently, a University of Maryland, Baltimore County postdoctoral fellow Sarah Stellwagen and her co-author Rebecca Renberg at the Army Research Lab have successfully published the complete sequences of genes that enable spiders to produce glue.
Spider glue is made of sticky silk and used by spiders to form webs for catching their prey. There are about 45,000 known species of spiders with each producing at least one type of silk. It is water soluble when it is still inside the spider’s body, then becomes insoluble to water after it has been produced outside the body. The unique characteristics of this material have piqued the interest of scientists.
Furthermore, the silk is also touted as the next breakthrough in making biomaterials due to its elasticity — making it flexible and able to absorb higher impact as well as it’s unusual tensile.
Because of the inimitable characteristic of silk being able to transform to a solid state from its liquid form inside the spider’s body, scientists find it challenging to reproduce. Scientists can recreate the liquid produced, but “we can’t replicate the process of going from liquid to solid on a large industrial scale,” Stellwagen says.
On the other hand, spider glue appears as a liquid, whether it is inside the spider’s body or outside—this may make it easier for scientists to produce spider glue in the laboratory compared to spider silk.
Throughout the years, researchers have been trying to unravel the secrets behind the spiders’ glue. Aside from being biodegradable and water-soluble, spider glue also remains sticky even after a long period and over many rounds of attachment and release.
Many species of spiders live in areas with humid conditions, yet surprisingly, spider glue still sticks firmly to wet surfaces. One goal of sequencing genes is for scientists to be able to create a synthetic version. These genes could be incorporated into the genes of other organisms such as bacteria and yeast to make the same glue.
Stellwagen sees a huge potential for spider glue to be used as organic pest control as it was, in the first place, produced to “capture insect prey.” Because it is an organic product, it could be applied without worrying about polluting the waterways compared to inorganic pesticides. It could be used on barn walls to protect livestock and sprayed on crops to prevent infestations. Also, it could be applied in areas where mosquito-borne illnesses are endemic.
Maximizing its features, scientists believe that there is a wide array of potentials for spider glue. It may lead to the development of bio-based adhesives and glues, referred to as “green glues,” which could replace petroleum-based products. Aside from organic pest control, it could be utilized as washable filters and mouse traps, among others.
Before this finding, the longest silk gene sequenced was approximately 20,000 base pairs. It took the researchers two years to completely sequence the genes. As what Stellwagen has said, “It ended up being this behemoth of a gene that’s more than twice as large as the previous largest silk gene.”
Aside from being remarkably long, the spider glue gene contained a lot of repetitive sequences in the middle, similar to the genes of spider silk. The numerous repetitive sequences posed a challenge to the researchers because of certain limitations in the methods they used. According to them, “It’s challenging. You’re picking a needle from a haystack.” Luckily, after two years of trying, they finally got the results that they needed to complete the sequence.
For many years, scientists have tried to sequence silk and glue genes. However, the task is challenging because of the length and repetitive structure of their sequences. “I’m super excited that I was able to finally figure out the puzzle because it was just so hard,” Stellwagen says. “Ultimately, we learned a lot, and I am happy to put that out there for the next person who is trying to solve some ridiculous gene.”
Currently, there are only about 20 complete genes that have been successfully sequenced, but there are a lot more genes out there that are still waiting to be sequenced. Thus, this recent finding has become a huge step in the sequencing or more silk and glue genes that could lead us to discover better and more efficient biomaterials.