Functional Amyloids as Key Biofilm Matrix Components

Amyloids are insoluble protein aggregates characterized by a cross β-sheet structure composed of repetitively stacked β-strands that form long fibrils. Often amyloids are considered in the context of neurodegenerative diseases such as Alzheimer’s disease. However, in some contexts, amyloids also play beneficial roles, and these amyloids are termed “functional amyloids.” Many bacteria produce functional amyloids, which facilitate biofilm formation by serving as a protein scaffold within the biofilm matrix. Within biofilms, amyloids help the bacteria to withstand environmental stresses and sustain biofilm growth. In this chapter, we explore the discovery and functions of bacterial amyloids, with a specific focus on those that play a role in biofilms. We also discuss how these proteins are recognized by the immune system.