Isolation, characterization, and aggregation of a structured bacterial matrix precursor

J Biol Chem. 2013 Jun 14;288(24):17559-68. doi: 10.1074/jbc.M113.453605. Epub 2013 Apr 30.


Biofilms are surface-associated groups of microbial cells that are embedded in an extracellular matrix (ECM). The ECM is a network of biopolymers, mainly polysaccharides, proteins, and nucleic acids. ECM proteins serve a variety of structural roles and often form amyloid-like fibers. Despite the extensive study of the formation of amyloid fibers from their constituent subunits in humans, much less is known about the assembly of bacterial functional amyloid-like precursors into fibers. Using dynamic light scattering, atomic force microscopy, circular dichroism, and infrared spectroscopy, we show that our unique purification method of a Bacillus subtilis major matrix protein component results in stable oligomers that retain their native α-helical structure. The stability of these oligomers enabled us to control the external conditions that triggered their aggregation. In particular, we show that stretched fibers are formed on a hydrophobic surface, whereas plaque-like aggregates are formed in solution under acidic pH conditions. TasA is also shown to change conformation upon aggregation and gain some β-sheet structure. Our studies of the aggregation of a bacterial matrix protein from its subunits shed new light on assembly processes of the ECM within bacterial biofilms.

Keywords: Amyloid Precursor Protein; Bacillus; Biofilm; Extracellular Matrix; Extracellular Matrix Proteins; Microbiology; Protein Aggregation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adsorption
  • Aluminum Silicates / chemistry
  • Amyloid / chemistry
  • Amyloid / isolation & purification
  • Amyloid / ultrastructure
  • Bacillus subtilis / physiology*
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / isolation & purification
  • Bacterial Proteins / ultrastructure
  • Biofilms*
  • Extracellular Matrix Proteins / chemistry*
  • Extracellular Matrix Proteins / isolation & purification
  • Extracellular Matrix Proteins / ultrastructure
  • Hydrogen-Ion Concentration
  • Hydrophobic and Hydrophilic Interactions
  • Light
  • Microscopy, Atomic Force
  • Particle Size
  • Protein Multimerization
  • Scattering, Radiation
  • Spectroscopy, Fourier Transform Infrared
  • Surface Properties


  • Aluminum Silicates
  • Amyloid
  • Bacterial Proteins
  • Extracellular Matrix Proteins
  • TasA protein, Bacillus subtilis
  • mica