Salmon skin is coated in a layer of mucus, the first line of defense against pathogens in the environment. The mucus is an interactive biological surface that traps pathogens and has antimicrobial activity. At the same time, the mucus is colonized by a distinct microbiota, similar to what we find in the gut (1). Studies of gut mucus revealed that the presence of bacteria is needed to achieve complete barrier function (2). Salmon skin mucus is an easy available surface for studies because it is external. It also represents an ancient vertebrate mucosal surface that has functional and structural similarities to the intestinal mucosa of mammals (3). This project has looked at the skin mucosa of germ-free and conventionally reared salmon to characterize the mucosal surface and understand how the presence of commensals can influence the barrier and ability to resist pathogen infection. A better understanding of natural mucosal surfaces could enable better synthetic mucus for therapeutic uses. Using AFM to probe the surface enables study of the barriers mechanical and interactive properties on the molecular level. Studies have looked at how bacteria bind to mucins (4, 5), but few studies have looked at the intact mucosal surfaces in their natural state. A novel method in this project is using AFM to look at nanoscale characteristics of these surfaces in situ, which could give new knowledge about the role of mucus organization.
1. Gomez D, Sunyer JO, Salinas I. The mucosal immune system of fish: the evolution of tolerating commensals while fighting pathogens. Fish & shellfish immunology. 2013;35(6):1729-39.
2. Meisel JS, Sfyroera G, Bartow-McKenney C, Gimblet C, Bugayev J, Horwinski J, et al. Commensal microbiota modulate gene expression in the skin. Microbiome. 2018;6(1):20.
3. Jin C, Padra JT, Sundell K, Sundh H, Karlsson NG, Linden SK. Atlantic Salmon Carries a Range of Novel O-Glycan Structures Differentially Localized on Skin and Intestinal Mucins. Journal of proteome research. 2015;14(8):3239-51.
4. Le DTL, Tran T-L, Duviau M-P, Meyrand M, Guérardel Y, Castelain M, et al. Unraveling the Role of Surface Mucus-Binding Protein and Pili in Muco-Adhesion of Lactococcus lactis. PLOS ONE. 2013;8(11):e79850.
5. Gunning A, Kavanaugh D, Thursby E, Etzold S, MacKenzie D, Juge N. Use of Atomic Force Microscopy to Study the Multi-Modular Interaction of Bacterial Adhesins to Mucins. International Journal of Molecular Sciences. 2016;17(11):1854.