The CUP pilus SMF-1 utilizes a specific antiparallel bundling mechanism to initiate biofilm formation.

SMF-1 pilus forms antiparallel bundles that facilitate rapid biofilm initiation in Stenotrophomonas maltophilia, revealing a unique structural mechanism for bacterial colonization.

• Why it matters: Understanding biofilm formation is crucial because it enhances bacterial resistance to environmental stresses and antibiotics, especially in pathogenic contexts like cystic fibrosis airways.
• What they did: Using 4.0 Å cryo-EM, the study determined that SMF-1 assembles into zigzag filaments that pair into antiparallel "pili couples" and higher-order bundles, despite lacking typical rod-like interfaces.
• The result: This structural insight uncovers a convergently evolved, archaic-like bundling mechanism that, combined with motility, accelerates cell aggregation and biofilm development, informing potential anti-biofilm strategies.