Elasticity and wrinkled morphology of Bacillus subtilis pellicles

M. TREJO; C. DOUARCHE; V. BAILLEUX; C. POULARD; C. REGEARD; S. MARIOT; E. RASPAUD

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Lugar: Washington DC, USA; Año: 2013 vol. 110 p. 2011 - 2016

0027-8424

Wrinkled morphology is a distinctive phenotype observed in maturebiofilms produced by a great number of bacteria. Here we study theformation of macroscopic structures (wrinkles and folds) observedduring the maturation of Bacillus subtilis pellicles in relation to theirmechanical response. We show how the mechanical buckling instabilitycan explain their formation. By performing simple tests, wehighlight the role of confining geometry and growth in determiningthe symmetry of wrinkles. We also experimentally demonstrate thatthe pellicles are soft elastic materials for small deformations inducedby a tensile device. The wrinkled structures are then described byusing the equations of elastic plates, which include the growth processas a simple parameter representing biomass production. Thisgrowth controls buckling instability, which triggers the formation ofwrinkles. We also describe how the structure of ripples is modifiedwhen capillary effects are dominant. Finally, the experiments performedon a mutant strain indicate that the presence of an extracellularmatrix is required to maintain a connective and elastic pellicle.