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 found no inhibition zones, indicating the absence of antibacterial properties. We also cultured all bacteria directly upon silk in Luria-Bertani broth (full nutrients), Phosphate-buffered saline (no nutrients) and nitrogen-free glucose broth (full nutrients, no nitrogen), and found bacteria grew readily on LB broth but not in PBS or NFG buffer. Our results indicated that spider silk's resistance to bacterial degradation is likely due to bacteriostatic, rather than antibacterial, mechanisms, as nitrogen is made unavailable.

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