Supramolecular organization in streptococcal pericellular capsules is based on hyaluronan tertiary structures

• Published in: Experimental cell research 2003-04, Vol.285 (1), p.1-8
• Main Authors: Scott, John E, Thomlinson, Alison M, Prehm, Peter
• Format: Article
• Language: English
• Subjects: Bacterial Capsules - chemistry; Bacterial Capsules - ultrastructure; Carbohydrate Conformation; Chondroitin Sulfates - metabolism; Chondroitin-4-sulfate; Critical electrolyte concentration (CEC); Cupromeronic blue; Extracellular matrix; Hyaluronic Acid - chemistry; Hyaluronic Acid - metabolism; Hyaluronoglucosaminidase - metabolism; Indicators and Reagents - metabolism; Indoles - metabolism; Organometallic Compounds - metabolism; Pneumococcal type 3 polysaccharide; Polysaccharides - chemistry; Polysaccharides - metabolism; Streptococcus; Streptococcus - ultrastructure; Streptococcus pneumoniae; β sheets
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1016/S0014-4827(02)00088-5

Supramolecular organization involving a polyanionic glycan in a bacterial capsule (hyaluronan, HA, in streptococcal capsules) is revealed, for the first time, by electron-histochemical methodology previously used to elucidate ultrastructure in extracellular matrix. Capsular HA filaments thereby revealed closely resemble aligned linear structures demonstrated by similar technology in HA solution. These parallel arrays, spontaneously formed, are based on HA tertiary structures (β sheet-like) which are stabilized by hydrophobic and hydrogen bonds. HA tertiary structures in aqueous solutions resist shear stress as shown by rheo-NMR. Thus, supramolecular HA wrapping covering many cells probably stabilizes chains of bacteria. Streptococci possibly templated the ordered structures since eukaryotic B6 cell HA did not produce similarly organized envelopes. Supramolecular organization in streptococcal and pneumococcal capsules are compared. Their glycans are very similar but the potential for HA-like tertiary structures is not present in the pneumococcal type 3 polysaccharide and chains of cells are not formed to the same extent by pneumococci. We suggest that the streptococcal capsule exemplifies a simple extracellular matrix analogous to those in animal connective tissues, which contain glycans (chondroitin, keratan, and dermochondan sulfates) of the HA family, capable of undergoing aggregation to similar tertiary structures.