Figure 1.
Gut epithelial cells and the host immune system recognize curli fibers.
Salmonella and E. coli are intestinal-dwelling bacteria whose curli fibers are recognized by host epithelial cells. The TLR1/2 heterocomplex recognizes the mature curli fiber and causes a signaling cascade in host cells. Recognition of curli results in an increase in PI3K in gut epithelial cells and increases gut epithelial cell barrier formation. Curliated Salmonella elicit an increase in cytokine production by T cells and dendritic cells. Salmonella curli mutants cause decreased epithelial cell barrier formation and lead to increased extraintestinal titers of Salmonella.
Figure 2.
Bacterial amyloids are utilized in multiple environments.
A) E. coli UPEC (UTI89) rugose biofilms form a complex spreading and wrinkling pattern that is dependent on the biofilm regulator CsgD. csgD mutant colonies do not spread or wrinkle. B) Curli are utilized by E. coli for increased adherence to lettuce roots and spinach leaves. Bacillus subtilis amyloid fiber proteins and biofilm formation are induced in the presence of tomato plant root exudate.