Nitrogen unavailability helps to protect spider silk from bacterial growth

Shichang Zhang, Dakota Piorkowski, Wan-Rou Lin, Yi-Ru Lee, Chen-Pan Liao, Pi-Han Wang, I-Min Tso
2019 Journal of Experimental Biology  
Spider silks are protein-based fibers that are incorporated into webs with the unique combination of high mechanical toughness and resistance to microbial degradation. While spiders are undoubtedly exposed to saprophytic microorganisms in their native habitats, such as the forest understory and bush, their silks have rarely been observed to decompose in either field or laboratory studies. We performed cross-streaking assays using silk from three spider species and four bacterial strains and
more » ... ial strains and found no inhibition zones, indicating the absence of antibacterial properties. We also cultured all bacteria directly upon silk in Luria-Bertani (LB) broth (full nutrients), phosphate-buffered saline (PBS; no nutrients) and nitrogen-free glucose broth (NFG; full nutrients, no nitrogen), and found that bacteria grew readily on silk in LB broth but not in PBS or NFG buffer. Our results indicate that spider silk's resistance to bacterial degradation is likely due to bacteriostatic rather than antibacterial mechanisms when nitrogen is inaccessible.
doi:10.1242/jeb.214981 pmid:31562186 fatcat:wznn22fg4facxdxug44umszl6y