Evidence for antimicrobial activity associated with common house spider silk

Abstract

BackgroundSpider silk is one of the most versatile materials in nature with great strength and flexibility. Native and synthetically produced silk has been used in a wide range of applications including the construction of artificial tendons and as substrates for human cell growth. In the literature there are anecdotal reports that suggest that native spider silk may also have antimicrobial properties.FindingsIn this study we compared the growth of a Gram positive and a Gram negative bacterium in the presence and absence of silk produced by the common house spider Tegenaria domestica. We demonstrate that native web silk of Tegenaria domestica can inhibit the growth of the Gram positive bacterium, Bacillus subtilis. No significant inhibition of growth was detected against the Gram negative bacterium, Escherichia coli. The antimicrobial effect against B. subtilis appears to be short lived thus the active agent potentially acts in a bacteriostatic rather than bactericidal manner. Treatment of the silk with Proteinase K appears to reduce the ability to inhibit bacterial growth. This is consistent with the active agent including a protein element that is denatured or cleaved by treatment. Tegenaria silk does not appear to inhibit the growth of mammalian cells in vitro thus there is the potential for therapeutic applications.

Facts and myths of antibacterial properties of silk

“…Similarly, Akiyama et al found the growth of gram positive bacteria on silk thread used for stitching mouse skin and as a result it created a membrane like structure. A recent study also suggested lack of bacterial growth of gram negative bacteria, E. coli on household spider silk . These contrasting reports suggest that protective role of sericin against bacteria is not very well understood and there could be influences from silk processing or experimental errors.…”

“…However, such studies on sericin have shown conflicting reports. Some studies suggested that sericin can evade the growth of Escherichia coli ( E. coli ), whereas others concluded that sericin helps to increase the E. coli growth …”

The Nephila clavipes genome highlights the diversity of spider silk genes and their complex expression

“…Spider silks can be stronger than steel and tougher than Kevlar, yet are much lighter weight than these manmade materials 4 . Silks vary in extensibility 5 , are temperature resilient 6 , can enable electrical conduction 7 , and can inhibit bacterial growth while being nearly invisible to the human immune system 8 . Thus, novel materials derived from spider silks offer tremendous potential for medical and industrial innovation.…”

Protease inhibitors in Bombyx mori silk might participate in protecting the pupating larva from microbial infection

“…Pupae inside the cocoons rarely suffer from disease or predation. The antimicrobial activity of silk produced by the common house spider Tegenaria domestica can be reduced or eliminated after digestion with protease K or soaking in water, suggesting that the antibacterial factors behaved as if they were soluble proteins (Wright & Goodacre, 2012). Previous studies of the antibacterial activity of silk have yielded conflicting results.…”

“…Previously, the antibacterial activity of silk, particularly the influence of sericin, was investigated (Pandiarajan et al, 2011;Wright & Goodacre, 2012); however, conflicting results have been obtained by previous studies on sericin. Previously, the antibacterial activity of silk, particularly the influence of sericin, was investigated (Pandiarajan et al, 2011;Wright & Goodacre, 2012); however, conflicting results have been obtained by previous studies on sericin.…”