Curli Amyloid Fibers in Escherichia coli Biofilms: The Influence of Water Availability on their Structure and Functional Properties

• Published in: Macromolecular bioscience 2024-02, Vol.24 (2), p.e2300234-n/a
• Main Authors: Siri, Macarena, Mangiarotti, Agustín, Vázquez‐Dávila, Mónica, Bidan, Cécile M.
• Format: Article
• Language: English
• Subjects: amyloid fibers; biofilm matrices; Biofilms; bio‐sourced materials; Coliforms; curli; E coli; Escherichia coli; Fibers; Growth conditions; Hydrophobicity; Material properties; Molecular structure; Polysaccharides; Rigidity; Saccharides; Spectroscopy; Substrates; Water availability
• ISSN: 1616-5187; 1616-5195
• DOI: 10.1002/mabi.202300234

Escherichia coli biofilms consist of bacteria embedded in a self‐produced matrix mainly made of protein fibers and polysaccharides. The curli amyloid fibers found in the biofilm matrix are promising versatile building blocks to design sustainable bio‐sourced materials. To exploit this potential, it is crucial to understand i) how environmental cues during biofilm growth influence the molecular structure of these amyloid fibers, and ii) how this translates at higher length scales. To explore these questions, the effect of water availability during biofilm growth on the conformation and functions of curli is studied. Microscopy and spectroscopy are used to characterize the amyloid fibers purified from biofilms grown on nutritive substrates with different water contents, and micro‐indentation to measure the rigidity of the respective biofilms. The purified curli amyloid fibers present differences in the yield, structure, and functional properties upon biofilm growth conditions. Fiber packing and β‐sheets content correlate with their hydrophobicity and chemical stability, and with the rigidity of the biofilms. This study highlights how E. coli biofilm growth conditions impact curli structure and functions contributing to macroscopic materials properties. These fundamental findings infer an alternative strategy to tune curli structure, which will ultimately benefit engineering hierarchical and functional curli‐based materials. The curli amyloid fibers found in Escherichia coli biofilms are promising building blocks for designing sustainable bio‐sourced materials. Understanding how biofilm growth conditions influence the structure and functions of curli helps to exploit their potential. This work shows that water availability during biofilm growth affects the conformation of curli, which in turn contributes to the properties of curli‐based materials.