Biofilm Matrix Proteins

Abstract

Proteinaceous components of the biofilm matrix include secreted extracellular proteins, cell surface adhesins, and protein subunits of cell appendages such as flagella and pili. Biofilm matrix proteins play diverse roles in biofilm formation and dissolution. They are involved in attaching cells to surfaces, stabilizing the biofilm matrix via interactions with exopolysaccharide and nucleic acid components, developing three-dimensional biofilm architectures, and dissolving biofilm matrix via enzymatic degradation of polysaccharides, proteins, and nucleic acids. In this article, we will review functions of matrix proteins in a selected set of microorganisms, studies of the matrix proteomes of Vibrio cholerae and Pseudomonas aeruginosa, and roles of outer membrane vesicles and of nucleoid-binding proteins in biofilm formation.

Figure 1

Colony morphology of V. cholerae rugose variant and mutant strains unable to produce RbmA, RbmC and Bap1 matrix proteins. Bar = 0.5mm.

Figure 2

Domain organization of V. cholerae RbmA, Bap1 and RbmC. FnIII, fibronectin type III; VCBS, Vibrio-Colwellia-Bradyrhizobium-Shewanella repeat; FG-GAP, phenyl-alanyl-glycyl (FG) and glycyl-alanyl-prolyl (GAP).

Figure 3

Domain organization of S. aureus Bap and S. enterica BapA. EF-hand calcium-binding motifs EF1 to 4 in Bap are indicated. LPxTG is the cell-wall anchoring motif. The repeats in the core regions of S. enterica BapA shares 29% identity with the C repeats of S. aureus Bap.