Amyloid fibers provide structural integrity to Bacillus subtilis biofilms.
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.
Romero
Diego
D
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115, USA.
Aguilar
Claudio
C
Losick
Richard
R
Kolter
Roberto
R
D000682:Amyloid / Q000737:chemistry* / Q000648:ultrastructure; D001412:Bacillus subtilis / Q000502:physiology* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology* / Q000648:ultrastructure; D018441:Biofilms; D055598:Chemical Phenomena; D004396:Coloring Agents; D003224:Congo Red; D046529:Microscopy, Electron, Transmission; D055503:Protein Multimerization
D000682:Amyloid; D001426:Bacterial Proteins; D004396:Coloring Agents; C119938:TasA protein, Bacillus subtilis; D003224:Congo Red