MICROBIAL EXOPOLYSACCHARIDES - STRUCTURAL SUBTLETIES AND THEIR CONSEQUENCES

Microbial extracellular heteropolysaccharides are mainly linear molecu les to which side chains of varying length and complexity are attached at regular intervals. Examination of 'families' of microbial exopolys accharide with closely related structures enables us to determine the effect of minor (or major) changes to structure on the physical proper ties of these macromolecules. Changes may also be seen in some of the biological properties of the polysaccharides, such as susceptibility t o enzymes; interaction with antibodies or lectins; and capacity and sp ecificity of ion binding. Acetyl groups frequently assert very marked effects on the properties of microbial polysaccharides. The presence o r absence of an O-acetyl or pyruvate (ketal) group on each oligosaccha ride repeat unit can greatly alter the properties of a number of exopo lysaccharides.