Laboratoire de Physique des Solides - UMR 8502

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Biomechanics of biofilms

 

Biofilms are living systems with a heterogeneous and multicomponent structure. This makes challenging the understanding of their mechanical properties as compared to other inert and homogeneous materials. We are currently studying their mechanical behaviors, how they may be compared to the other systems or described by simple laws. Most of the work is done on biofilms named pellicles standing on the top of liquid, at the air-liquid interface, and on biofilms formed by Bacillus subtilis.

 

Our first study, published in 2013, focussed on the mechanical forces determining the biofilm morphologies at a macroscopic scale. Wrinkled morphology is a distinctive phenotype observed in mature biofilms produced by a great number of bacteria. We have shown how these ripples might be explained by the buckling mechanical instability and hypothesized the presence of stress inside the biofilm. In a further paper (2015), we have explicitly shown the existence of a growth stress within the pellicles : bacteria multiply and secrete extracellular matrix in a confined environment which generate a compressive force.
As pellicles are pre-stressed due this growth, it was interesting to study how they would response to mechanical strain (2016). Based on the response to cyclic stimuli, we arrived to the conclusion that they are elastic in the compressive regime while being plastic in the tensile regime.

 

Related links :
 

https://www.lps.u-psud.fr/spip.php?article2706&lang=en

 

 

This video shows examples of biofilm reorganization after the puncturing of compressed (A) and released (B) pellicles. The internal compression helps maintain the biofilm integrity. Scale bars represent 2 mm.