A major component of bacterial biofilms is curli amyloid fibrils secreted by the 
curli biogenesis system. Understanding the curli biogenesis mechanism is 
critical for developing therapeutic agents for biofilm-related infections. Here 
we report a systematic study of the curli biogenesis system, highlighted by 
structural, biochemical and functional analysis of the secretion channel 
complexes (CsgF-CsgG) with and without the curli substrate. The dual-pore 
architecture of the CsgF-CsgG complex was observed and used to develop an 
approach to inhibit the curli secretion by physically reducing the size of the 
CsgF pore. We further elucidated the assembly of the CsgFG complex with curli 
components (CsgA and CsgB) and curli-cell association through CsgF. Importantly, 
the recognition of the CsgA substrate by CsgG was uncovered. Nine crevices 
outside of the CsgG channel provide specific and highly-conserved recognition 
sites for CsgA N-terminus. Together with analysis of CsgE, our study provides 
comprehensive insights into curli biogenesis.