An Updated Classification System and Review of the Lipooligosaccharide Biosynthesis Gene Locus in .

Lipooligosaccharide (LOS) is an integral component of the cell membrane with a structure of core oligosaccharides forming inner and outer core regions and a lipid A moiety. The gene content of the LOS core biosynthesis cluster exhibits extensive sequence variation, which leads to the production of variable cell surface LOS structures in . Some LOS outer core molecules in are molecular mimics of host structures (such as neuronal gangliosides) and are thought to trigger neuronal disorders (particularly Guillain-Barré syndrome and Miller Fisher syndrome) in humans. The extensive genetic variation in the LOS biosynthesis gene cluster, a majority of which occurs in the LOS outer core biosynthesis gene content present between and , has led to the development of a classification system with 23 classes (A-W) and four groups (1-4) for the LOS region. This review presents an updated and simplified classification system for LOS typing alongside an overview of the frequency of LOS biosynthesis genotypes and structures in various populations.