title: Direct Comparison of Physical Properties of Bacillus subtilis NCIB 3610 and B-1 Biofilms.
abstract: Many bacteria form surface-attached communities known as biofilms. Due to the extreme resistance of these bacterial biofilms to antibiotics and mechanical stresses, biofilms are of growing interest not only in microbiology but also in medicine and industry. Previous studies have determined the extracellular polymeric substances present in the matrix of biofilms formed by Bacillus subtilis NCIB 3610. However, studies on the physical properties of biofilms formed by this strain are just emerging. In particular, quantitative data on the contributions of biofilm matrix biopolymers to these physical properties are lacking. Here, we quantitatively investigated three physical properties of B. subtilis NCIB 3610 biofilms: the surface roughness and stiffness and the bulk viscoelasticity of these biofilms. We show how specific biomolecules constituting the biofilm matrix formed by this strain contribute to those biofilm properties. In particular, we demonstrate that the surface roughness and surface elasticity of 1-day-old NCIB 3610 biofilms are strongly affected by the surface layer protein BslA. For a second strain,B. subtilis B-1, which forms biofilms containing mainly γ-polyglutamate, we found significantly different physical biofilm properties that are also differently affected by the commonly used antibacterial agent ethanol. We show that B-1 biofilms are protected from ethanol-induced changes in the biofilm's stiffness and that this protective effect can be transferred to NCIB 3610 biofilms by the sole addition of γ-polyglutamate to growing NCIB 3610 biofilms. Together, our results demonstrate the importance of specific biofilm matrix components for the distinct physical properties of B. subtilis biofilms.
authors.affiliation: Center for NanoScience, Faculty of Physics, Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: Sara
authors.initials: S
authors.lastname: Kesel
authors.affiliation: Institute of Medical Engineering and Department of Mechanical Engineering, Technische Universität München, Garching, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Grumbein
authors.affiliation: Center for NanoScience, Faculty of Physics, Ludwig-Maximilians-Universität München, Munich, Germany.
authors.forename: Ina
authors.initials: I
authors.lastname: Gümperlein
authors.affiliation: Institute of Medical Engineering and Department of Mechanical Engineering, Technische Universität München, Garching, Germany.
authors.forename: Marwa
authors.initials: M
authors.lastname: Tallawi
authors.affiliation: Department of Applied Physics and Center for NanoScience, Ludwig-Maximilians-Universität, Munich, Germany.
authors.forename: Anna-Kristina
authors.initials: AK
authors.lastname: Marel
authors.affiliation: Institute of Medical Engineering and Department of Mechanical Engineering, Technische Universität München, Garching, Germany oliver.lieleg@tum.de opitz@physik.uni-muenchen.de.
authors.forename: Oliver
authors.initials: O
authors.lastname: Lieleg
authors.affiliation: Center for NanoScience, Faculty of Physics, Ludwig-Maximilians-Universität München, Munich, Germany oliver.lieleg@tum.de opitz@physik.uni-muenchen.de.
authors.forename: Madeleine
authors.initials: M
authors.lastname: Opitz
mesh_terms: D001412:Bacillus subtilis / Q000378:metabolism / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development*; D055592:Biophysical Phenomena; D001704:Biopolymers / Q000032:analysis*; D004548:Elasticity; D013499:Surface Properties
chemical_list: D001704:Biopolymers