Abstract
Collagen layer moisturized by Staphylococcus epidermidis on the skin, protects our body from external pathogens. Moreover, S. epidermidis is well known to contribute to our innate immune system. However, the relationship between vertebrate collagen and the symbiotic bacterium, has not been studied to date. Here, we observed development of S. epidermidis colonies on collagen substrate using liquid-phase atmospheric scanning electron microscopy (ASEM). Biofilms were formed on thin-film-windowed ASEM specimen holders with or without collagen coating, fixed by aldehyde, and observed in aqueous buffer using ASEM. Amazingly, an intensive spider-web-like biofilm was constructed on collagen-coated film, whereas flat biofilm on non-coated film. During the process, bacterial cells first adhered to the collagen substrate, multiplied rapidly, secreted micro vesicles, formed delicate web-like intercellular fibril connections, and surrounded by extracellular polymeric substance matrix. Their firm attachment to collagen substrate suggests involvement of the hypothesized collagen-binding proteins. The web-like biofilm of S. epidermidis bacteria in response to collagen, could reflect their life from on vertebrate skin, which could be acquired during the symbiosis. The structure seems to be advantageous to moisturize our skin, and could be important to understanding their role for our innate immune system and further pathogenic processes of the related infectious diseases.