Fluorescence and NMR spectroscopy together with molecular simulations reveal amphiphilic characteristics of a Burkholderia biofilm exopolysaccharide

Abstract

Biofilms are a collective mode of bacterial life in which a self-produced matrix confines cells in close proximity to each other. Biofilms confer many advantages, including protection from chemicals (including antibiotics), entrapment of useful extracellular enzymes and nutrients, as well as opportunities for efficient recycling of molecules from dead cells. Biofilm matrices are aqueous gel-like structures composed of polysaccharides, proteins, and DNA stabilized by intermolecular interactions that may include non-polar connections. Recently, polysaccharides extracted from biofilms produced by species of the complex were shown to possess clusters of rhamnose, a 6-deoxy sugar with non-polar characteristics. Molecular dynamics simulations are well suited to characterizing the structure and dynamics of polysaccharides, but only relatively few such studies exist of their interaction with non-polar molecules. Here we report an investigation into the hydrophobic properties of the exopolysaccharide produced by strain C1576. Fluorescence experiments with two hydrophobic fluorescent probes established that this polysaccharide complexes hydrophobic species, and NMR experiments confirmed these interactions. Molecular simulations to model the hydrodynamics of the polysaccharide and the interaction with guest species revealed a very flexible, amphiphilic carbohydrate chain that has frequent dynamic interactions with apolar molecules; both hexane and a long-chain fatty acid belonging to the quorum-sensing system of were tested. A possible role of the non-polar domains of the exopolysaccharide in facilitating the diffusion of aliphatic species toward specific targets within the biofilm aqueous matrix is proposed.

Comparative Study of Immunogenic Properties of Purified Capsular Polysaccharides fromStreptococcus suisSerotypes 3, 7, 8, and 9: the Serotype 3 Polysaccharide Induces an Opsonizing IgG Response

“…Taken together, our results suggest that purified CPS 3 possesses unique structural and/or biochemical properties. In this regard, it was observed that water soluble CPS 3 was precipitated in the presence of the detergent sodium deoxycholate, suggesting an amphiphilic character for this polysaccharide ( 56 ). The hydrophobic element is most likely the di- N -acetylated d -bacillosamine, as acetylation increases hydrophobicity (such as is the case for chitin versus chitosan [ 57 ]), which is then linked to the negatively charged d -glucuronic acid, together forming the amphiphilic disaccharide repeating unit of CPS 3 ( Fig.…”

Multifrequency STD NMR Unveils the Interactions of Antibiotics With Burkholderia multivorans Biofilm Exopolysaccharide

“…We first wanted to probe the feasibility of the STD NMR approach for this type of interaction. The hydrophobic properties of EpolC1576 have been previously studied through its interactions with small molecules as 2-(p-toluidinyl)-naphthalene-6-sulfonate (TNS) and 1-anilinonaphthalene-8-sulfonate (ANS) ( Kuttel et al, 2017 ). In that study, interactions of both compounds with EpolC1576 were demonstrated by simple observation of line broadening in the NMR spectra of ANS and TNS in the presence of EpolC1576, in contrast to the sharp lines observed in the negative control experiments in the presence of dextran, suggesting interactions taking place with EpolC1576 and them being within the so-called fast exchange regime.…”

Predicting the Structures of Glycans, Glycoproteins, and Their Complexes

“…Although significant for many diseases, from cystic fibrosis 180,181 to endocarditis, 182 the complex calcium-mediated aggregation of polysaccharide biofilms represents a particularly challenging class of structure to model. 183,184…”