BIOSYNTHESIS OF THE POLYSIALIC ACID CAPSULE IN ESCHERICHIA-COLI K1

The extracellular polysaccharides elaborated by most or all bacterial species function in cell-to-cell and cell-substratum adhesion, cell si gnaling, and avoidance or inhibition of noxious agents in animal hosts or free-living environments. Recent advances in our understanding of exopolysaccharide synthesis have been facilitated by comparative appro aches in both plant and animal pathogens, as well as in microorganisms of industrial importance. One of the best understood of these systems is the kps locus for polysialic acid synthesis in Escherichia coli K1 . The genes for sialic acid synthesis, activation, polymerization and translocation have been identified and assigned at least tentative fun ctions in the synthetic and export pathways. Initial studies of kps th ermoregulation suggest that genetic control mechanisms will be involve d which are distinct from those already described for several other ex opolysaccharides. Information about the common as well as unique featu res of polysialic acid biosynthesis will increase our knowledge of mic robial cell surfaces which in turn may suggest novel targets for thera peutic or industrial interventions.