Amyloid fibers provide structural integrity to Bacillus subtilis biofilms

• Published in: Proceedings of the National Academy of Sciences - PNAS 2010-02, Vol.107 (5), p.2230-2234
• Main Authors: Romero, Diego, Aguilar, Claudio, Losick, Richard, Kolter, Roberto
• Format: Article
• Language: English
• Subjects: Amyloid - chemistry; Amyloid - ultrastructure; Amyloids; Antibodies; Bacillus subtilis; Bacillus subtilis - physiology; Bacillus subtilis - ultrastructure; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - physiology; Bacterial Proteins - ultrastructure; Biofilms; Biological Sciences; Cells; Chemical Phenomena; Coloring Agents; Congo Red; Dyes; Extracellular matrix; Fimbriae; Kinetics; Matrix; Medical treatment; Microscopy, Electron, Transmission; Mutation; Polymerization; Protein Multimerization; Proteins
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0910560107

Bacillus subtilis forms biofilms whose constituent cells are held together by an extracellular matrix. Previous studies have shown that the protein TasA and an exopolysaccharide are the main components of the matrix. Given the importance of TasA in biofilm formation, we characterized the physicochemical properties of this protein. We report that purified TasA forms fibers of variable length and 10-15 nm in width. Biochemical analyses, in combination with the use of specific dyes and microscopic analyses, indicate that TasA forms amyloid fibers. Consistent with this hypothesis, TasA fibers required harsh treatments (e.g., formic acid) to be depolymerized. When added to a culture of a tasA mutant, purified TasA restored wild-type biofilm morphology, indicating that the purified protein retained biological activity. We propose that TasA forms amyloid fibers that bind cells together in the biofilm.