No evidence spider silk is antibacterial, study finds

Spider silk may not be as magical a substance as we’ve been led to believe, new research suggests. Scientists closely examined the silk of several different spiders, but could not find any with antimicrobial properties. The researchers say their findings should challenge previous claims that antibacterial spider silk has been found and that antibiotic silk should only be seen as a myth.

Spider silk has long fascinated scientists and the public. The sticky substance, a protein fiber, is made by all known spiders, although its uses vary widely from species to species. There is of course the classic web, but some spiders also use silk as a net to catch their prey. Some species use it in their mating rituals, while the smaller ones float in the air on their strands. Others will be content to eat the silk that remains unused, as a sort of recycling. Given its versatility, it’s no surprise that humans in the past and present have tried to replicate the advantages of spider silk for ourselves.

A assumed attribute of silk is its antimicrobial activity, which has attracted the interest of researchers from Aarhus University in Denmark. Social spiders live in tight-knit communities with little genetic diversity, conditions that make them ripe for rapidly spreading epidemics of infectious disease. But if silk acts as a sort of antibiotic barrier, they theorized, it could help explain why these spiders survive as well as they do. More hopefully, this could mean that there are unique compounds that scientists could one day adapt from silk to antibiotics for human use, something we have long done with other natural sources.

Researchers continued to keep it short, however. No matter what species or germ they used it against, the silk just didn’t seem anti-bacterial at all. And once it was clear where things were heading, they started digging deeper.

“We were unable to detect antimicrobial activity in social spider silk, which made us curious as to why other studies were able to detect antimicrobial activity in spider silk. Then we started. to review the articles reporting antimicrobial activity in great detail and realize the methodological shortcomings, ”study lead author Trine Bilde, evolutionary biologist at Aarhus, told Gizmodo.

For one thing, there just wasn’t a lot of research on the topic in the first place, with many claims representing little more than anecdotal evidence. And among the few articles that found some effect, the team spotted a few possible fatal flaws. Some studies, for example, apparently did not attempt to account for bacterial contamination of samples, which could have affected the growth of other bacteria that the scientists were actually studying. Many also didn’t seem to be trying to control the effects of the solvents used to extract spider silk, some of which are known to have their own antibacterial properties, like ethyl acetate.

A crucial part of scientific research is replication. And when Bilde and her team conducted experiments with seven different types of spider silk that had antimicrobial activity in the past, they found no activity at that time. The results of their article – titled “The Myth of Antibiotic Spider Silk” – were published Tuesday in iScience.

Despite this title, Bilde does not completely close the door to this area of ​​research. It is possible that one day other scientists will stumble upon the antimicrobial silk of a specific spider or debunk this debunking. But for now, she said, skepticism should be the rule by default and future studies should be designed to avoid errors documented by her team. “We can always test the idea on new species and with new test microbes, but with a more careful starting point,” she said.

It is also possible that silk is not totally useless against germs. Since silk is commonly used to protect spider eggs, easy prey for some bacteria and fungi, Bilde noted, it may still have properties that act as a physical barrier against disturbing germs. Some research has suggested that this might explain why silk remains rot-free for so long. Other scientists have created synthetic silk which can be infused with the existing antibiotics, in the hope of someday developing improved dressings.

As with all Tobey Maguire fans out there as Spider-Man fans, don’t worry: the list of things Spider Silk can do is still very long.

“Spider silk has extraordinary properties,” said Bilde. “There are many other functions still unknown and worth investigating, such as the strength and elasticity of silk, properties that would be useful in developing more applied applications. “