Spider web silk has been used as a remedy to treat skin lesions to warts for centuries since ancient Rome for its alleged antibiotic effects, but researchers have now reviewed old experiments and disprove that myth of the antibiotic spider web, as published in the journal ‘iScience’.
In the past, doctors covered open wounds with spider webs or they advised patients to place the cocoons on infected teeth. However, in modern times, the literature contains conflicting reports on whether or not spider silk has antimicrobial properties.
“Spider silk has always been admired and almost has a mythical status,” explains lead author Trine Bilde, a professor of biology at Aarhus University in Denmark. it seems to have been established by belief and not by strong empirical support. “
Since the antimicrobial properties of spider silk were first reported, researchers have proposed ways in which spiders could benefit. In the case of social spiders that live in large groups, it has been thought that antibiotic floss could help prevent the spread of infection between individuals. These spiders have a weakened immune system from inbreeding, making them especially vulnerable to infection.
Methodological deficiencies in previous articles studies
Early in their research, Bilde and his research group began to doubt the validity of what they had read in the literature. “We were unable to detect the antimicrobial activity of social spider silk, regardless of the method or the microbe, and this made us curious why other studies were able to do it. So we began to scrutinize the articles reporting antimicrobial activity in detail and we realized methodological shortcomings. ”
The researchers identified two categories of deficiencies in the published literature: on the one hand, the risk of bacterial contamination and, on the other, the inadequate control of the solvent used to extract the spider silk.
The team showed that previous reports were probably compromised, for example by having measured the effect of the solvent used to extract spider silk instead of the spider silk itself. Solvents such as acetone or ethyl acetate can have strong antimicrobial effects on their own.
Overall, Bilde’s team examined silk from seven different species of spiders using improved experimental methods and found no signs of antimicrobial activity. Although this does not rule out the antimicrobial activity of all spider species, it calls into question all previous reports.
“Instead of assuming that spider silk is antimicrobial, we should now assume that it is not,” says Bilde. “We can still test the idea in new species and with new organisms, but with a more cautious starting point.”
Spiders they use their silk to protect their eggs, which offer a high nutritional content to microbes. Bilde proposes that instead of warding off microbial threats with intrinsic antimicrobial activity, the silk sheath surrounding the eggs could function only as a physical barrier.