title: Structure and Dynamics of a Model Polymer Mixture Mimicking a Levan-Based Bacterial Biofilm of Bacillus subtilis.
abstract: In this paper, we report on the structure and dynamics of biologically important model polymer mixtures that mimic the extracellular polymeric matrix in native biofilm of Bacillus subtilis. This biofilm is rich in nonionic polysaccharide levan, but also contains other biopolymers such as DNA and proteins in small concentrations. Aiming to identify the contribution of each component to the formation of the biofilm, our investigations encompassed dynamic rheology, small-angle X-ray scattering, dynamic light scattering, microscopy, densitometry, and sound velocity measurements. As it turned out, this very powerful combination of techniques is able to provide solid results on the dynamical and structural aspects of the microbiologically and chemically complex biofilm formations. Macroscopic rheological measurements revealed that the addition of DNA to levan solution increased the viscosity, pseudoplasticity, and elasticity of the system. The addition of protein contributed similarly, but also increased the rigidity of the system. This confirms that the presence of minor biofilm components is essential for biofilm formation. DNA and proteins appear to confine levan molecules within their supramolecular structure and, in this way, restrict the role of levan to merely a filling agent. These findings were complemented by small-angle X-ray scattering data, which provided insight into the structure on a molecular scale. One of the essential goals of this work was to compare the structural properties of the native biofilm and synthetic biofilm mixture.
authors.affiliation: Faculty of Chemistry and Chemical Technology and Biotechnical Faculty, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors.forename: Elizabeta
authors.initials: E
authors.lastname: Benigar
authors.affiliation: Faculty of Chemistry and Chemical Technology and Biotechnical Faculty, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors.forename: Andreja
authors.initials: A
authors.lastname: Zupančič Valant
authors.affiliation: Biotechnical Faculty, University of Ljubljana , Večna pot 111, SI-1000, Ljubljana, Slovenia.
authors.forename: Iztok
authors.initials: I
authors.lastname: Dogsa
authors.affiliation: Biotechnical Faculty, University of Ljubljana , Večna pot 111, SI-1000, Ljubljana, Slovenia.
authors.forename: Simon
authors.initials: S
authors.lastname: Sretenovic
authors.affiliation: Biotechnical Faculty, University of Ljubljana , Večna pot 111, SI-1000, Ljubljana, Slovenia.
authors.forename: David
authors.initials: D
authors.lastname: Stopar
authors.affiliation: Faculty of Chemistry and Chemical Technology and Biotechnical Faculty, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors.forename: Andrej
authors.initials: A
authors.lastname: Jamnik
authors.affiliation: Faculty of Chemistry and Chemical Technology and Biotechnical Faculty, University of Ljubljana , Večna pot 113, SI-1000 Ljubljana, Slovenia.
authors.forename: Matija
authors.initials: M
authors.lastname: Tomšič
mesh_terms: D001412:Bacillus subtilis / Q000502:physiology*; D018441:Biofilms; D004247:DNA / Q000737:chemistry*; D005630:Fructans / Q000737:chemistry*; D012212:Rheology; D014961:X-Ray Diffraction
chemical_list: D005630:Fructans; D004247:DNA; C072599:levan