Bacterial Biofilms

In a time when bio-sourced materials are raising interest for their sustainability, harnessing the ability of bacteria to produce biofilms made of a protein and polysaccharide matrix has become a new strategy to produce “engineered living materials” with various functionalities. This emerging field of biomaterials science mostly focuses on the study and modification of the structural fibrous matrix to tune the properties of the final “product”, e.g. curli and cellulose fibres in E. coli. Independently, biophysical approaches have shown that specific bacterial adherence factors and interfacial interactions determine biofilm morphology. It is thus highly critical to understand how the interplay between structural and adherence factors forms a matrix that determines biofilm architecture and mechanics.

Left: Bacterial cells expressing fimbrial adhesins (TEM). Right. Image of E. coli AR3110 biofilm grown on a nutritive agar substrate.

The model bacterium E. coli expresses a wide array of surface adhesin proteins, some of which play an essential role in initial attachment to surfaces and others that promote biofilm growth by enabling cell-cell interactions and formation of bacterial aggregates at the early stages of biofilm formation. Biofilms also contain a diversity of adhesive polysaccharides that remain attached to the bacterial cell surface or are secreted as exopolysaccharides into the matrix.

While the role of the adhesive extracellular matrix in cellular mechanotransduction has been intensively studied in mammalian tissues, the mechanisms involved in bacterial mechanotransduction have hardly been investigated beyond the level of individual bacterial cells. Ultimately, understanding the specific role of adhesion in biofilm mechanobiology will help to design and grow biofilm-based materials with tunable stability and dynamics.

The leaders of the Biofilms research program at MPQC. Left: A/Prof Makrina Totsika (QUT). Right: Dr Cécile Bidan (MPICI). Centre: Mixed bacterial aggregates formed by the interaction of distinct adhesins, as imaged by fluorescence microscopy.

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