title: Elasticity and wrinkled morphology of Bacillus subtilis pellicles.
abstract: Wrinkled morphology is a distinctive phenotype observed in mature biofilms produced by a great number of bacteria. Here we study the formation of macroscopic structures (wrinkles and folds) observed during the maturation of Bacillus subtilis pellicles in relation to their mechanical response. We show how the mechanical buckling instability can explain their formation. By performing simple tests, we highlight the role of confining geometry and growth in determining the symmetry of wrinkles. We also experimentally demonstrate that the pellicles are soft elastic materials for small deformations induced by a tensile device. The wrinkled structures are then described by using the equations of elastic plates, which include the growth process as a simple parameter representing biomass production. This growth controls buckling instability, which triggers the formation of wrinkles. We also describe how the structure of ripples is modified when capillary effects are dominant. Finally, the experiments performed on a mutant strain indicate that the presence of an extracellular matrix is required to maintain a connective and elastic pellicle.
authors: Laboratoire de Physique des Solides, Université Paris-Sud,  Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8502, F-91405 Orsay,  France.
authors: Miguel
authors: M
authors: Trejo
authors: Carine
authors: C
authors: Douarche
authors: Virginie
authors: V
authors: Bailleux
authors: Christophe
authors: C
authors: Poulard
authors: Sandrine
authors: S
authors: Mariot
authors: Christophe
authors: C
authors: Regeard
authors: Eric
authors: E
authors: Raspaud
mesh_terms: D001412:Bacillus subtilis / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development*; D001696:Biomechanical Phenomena; D004548:Elasticity; D055641:Mathematical Concepts; D008954:Models, Biological; D010641:Phenotype