Functional Amyloids Regulate Microbial Cell Fate

In nature, bacteria form biofilms – multicellular differentiated communities. In a biofilm, cells use a variety of mechanisms to coordinate activity. Bacterial biofilms are of extreme clinical importance, as they are associated with many persistent and chronic bacterial infections. Amyloid-like proteins such as Curli (produced by Escherichia coli), and TasA (produced by Bacillus subtilis) are extremely common in bacterial biofilms and the assembly of the bacterial amyloid-like fibres is important for the integrity of biofilms. We utilized high resolution live microscopy to study the formation of microbial amyloids in B. subtilis, and to visualize single fibres during their formation. Furthermore, using transcriptional reporters and an unbiased transcriptome analysis of biofilm cells, we revealed highly specific effects of TasA amyloids on cell fate. In mostly sessile biofilms, TasA is a signal required for the expression of flagellar assembly genes and chemotaxis machinery. TasA acts as a secreted extracellular signal, and can restore the expression of motility genes to neighbour communities lacking TasA. Overall, our work discovered a signalling role for a microbial amyloid.