Synthetic phosphoethanolamine-modified oligosaccharides reveal the importance of glycan length and substitution in biofilm-inspired assemblies

Abstract

Bacterial biofilm matrices are nanocomposites of proteins and polysaccharides with remarkable mechanical properties. Efforts understanding and tuning the protein component have been extensive, whereas the polysaccharide part remained mostly overlooked. The discovery of phosphoethanolamine (pEtN) modified cellulose in E. coli biofilms revealed that polysaccharide functionalization alters the biofilm properties. To date, the pattern of pEtN cellulose and its mode of interactions with proteins remains elusive. Herein, we report a model system based on synthetic epitomes to explore the role of pEtN in biofilm-inspired assemblies. Nine pEtN-modified oligosaccharides were synthesized with full control over the length, degree and pattern of pEtN substitution. The oligomers were co-assembled with a representative peptide, triggering the formation of fibers in a length dependent manner. We discovered that the pEtN pattern modulates the adhesion of biofilm-inspired matrices, while the peptide component controls its stiffness. Unnatural oligosaccharides tune or disrupt the assembly morphology, revealing interesting targets for polysaccharide engineering to develop tunable bio-inspired materials.

Structural basis for synthase activation and cellulose modification in the E. coli Type II Bcs secretion system

“…In many free-living and eukaryotic host-associated bacterial species, secreted cellulosic polymers represent key building components in the three-dimensional architecture of collaborative multicellular biofilms 3,6 . In E. coli, the phosphoethanolamine decoration of secreted cellulose influences not only the physicochemical properties of the polymer itself, but also favors higherorder, long-range fibrillation of the other major biofilm matrix component -amyloid curli -and thus provides for markedly increased biofilm cohesion and elasticity 38,39 . Importantly, the mature biofilm is a highly heterogeneous environment with stark gradients of oxygen, nutrients, moisture and/or shear stress, which leads to local stratification and/or compartmentalization of the quantity and type of secreted adherence factors and yields to a self-organized division of labor among subsets of cells engaged in extracellular matrix production, while others provide for cell proliferation and biofilm dispersal 3,40 .…”

Tuning the Chiral Structures from Self‐Assembled Carbohydrate Derivatives

“…[49][50][51] Particularly, the size and length of the glycans have a significant impact on self-assembly and chiral expression. [52] Empirical strategies for designing carbohydrate derivatives are often to modify the hydroxyl groups on the carbon skeletons of saccharide ring with functional groups, such as lipid chains and aromatic segments to extend the intra/intermolecular interactions. Very recently, the formation of chiral, flower-like, or solid microparticles by only using monosaccharide stearoyl esters was reported for the first time.…”

“…[ 49–51 ] Particularly, the size and length of the glycans have a significant impact on self‐assembly and chiral expression. [ 52 ]…”

Deoxyfluorination tunes the aggregation of cellulose and chitin oligosaccharides and highlights the role of specific hydroxyl groups in the crystallization process

“…19,20 In contrast, bottom-up approaches guarantee precise saccharide sequences and patterns of modification, important determinants of the materials and biological properties. [21][22][23][24][25] Perturbing the primary sequence of an oligosaccharide with non-natural residues offers a strategy to systematically tune the macroscopic properties of a material. In addition, this approach provides indirect information on the role of the replaced unit (or functional group).…”

“…19,20 In contrast, bottom-up approaches guarantee precise saccharide sequences and patterns of modification, important determinants of the materials and biological properties. 21–25…”