Scl1-mediated model of GAS biofilm (not to scale). Scl1 hydrophobin (current study) initiates bacterial adhesion to animate surfaces  within the host (blue field). Scl1 adhesin anchors the growing microcolony by direct binding to tissue extracellular matrix (ECM) components, cellular fibronectin and laminin , initiating microcolony formation and anchoring the outside edge of GAS microcolony in tissue (yellow field). Microcolony scaffolding is stabilized by the formation of head-to-head dimers between Scl1 molecules on adjacent chains (pink field). Inset shows Scl1-Scl1 head-to-head dimers formed by rScl1.1 as viewed by electron microscopy after rotary shadowing . Bar: 50 nm.