Characterization of one of the most prevalent chaperone-usher fimbriae of E. coli

What is it about?

Initial adhesion of bacterial cells to surfaces or host tissues is a key step in colonisation and biofilm formation processes, and is mediated by cell surface appendages. It was previously demonstrated that Escherichia coli K-12 possesses an arsenal of silenced chaperone-usher fimbriae that were functional when constitutively expressed. Among them, production of prevalent Yad fimbriae induces adhesion to abiotic surfaces. Functional characterisation of Yad fimbriae were undertook, and YadN was identified as the most abundant and potential major pilin, and YadC as the potential tip-protein of Yad fimbriae. It was showed that Yad production participates to binding of E. coli K-12 to human eukaryotic cells (Caco-2) and inhibits macrophage phagocytosis, but also enhances E. coli K-12 binding to xylose, a major component of the plant cell wall, through its tip-lectin YadC. Consistently, it was demonstrated that Yad production provides E. coli with a competitive advantage in colonising corn seed rhizospheres. The latter phenotype is correlated with induction of Yad expression at temperatures below 37°C, and under anaerobic conditions, through a complex regulatory network. Taken together, these results suggest that Yad fimbriae are versatile adhesins that beyond potential capacities to modulate host–pathogen interactions might contribute to E. coli environmental persistence.

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Why is it important?

This work describes an in-depth characterization of one of the numerous fimbrial appendages displayed by E. coli at its cell-surface. It is shown that this fimbriae could have a dual role in the host and in the environment for persistence. This work points to the versality of the adhesins in E. coli and how E. coli can use these different adhesins to modulate its colonisation capacity in the host and in the environment.