Authors
Iarocci, J., Whitfield, G. B., Williston, R. F., Wozny, M. R., Presley, J. F., Ellison, C. K., Brun, Y. V., Guo, S.
Abstract
The Tight adherence (Tad) pilus is a broadly distributed and evolutionarily distinct subclass of type IV pili that mediates cell adhesion, biofilm formation, predation, and surface sensing in many bacteria, including Caulobacter crescentus, Myxococcus xanthus, Vibrio vulnificus, and Bifidobacterium breve. Tad pili undergo cycles of extension and retraction powered by a cell-envelope-embedded nanomachine. Despite their biological importance, the architecture and assembly mechanism of the Tad pilus system have remained poorly understood. Although cryo-electron tomography (cryo-ET) has elucidated the in situ structures of other type IV pilus systems, no intact Tad machine structure has previously been reported. Here, we use cryo-ET and subtomogram averaging to resolve the near-native architecture of the C. crescentus Tad pilus within the bacterial cell envelope. 3D classification further reveals multiple assembly intermediates, and integrative modelling incorporating AlphaFold3 predictions help define the spatial arrangement of all core components. The resulting structural framework gives insight into the stepwise assembly process of the C. crescentus Tad pilus machine. Altogether, our results provide an in situ architectural model of the Tad pilus machine, establishing a foundation for understanding homologous systems across a broad range of bacteria.
Preprint server:
bioRxiv
The authors list and abstract were imported from bioRxiv on 07 Nov 2025.
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