Predicting the Biological Repeating Unit of Bacterial Lipopolysaccharides: Common Structural Motifs in Regular Polysaccharides from Different Genera

The cell surface of most organisms is covered by carbohydrates linked to lipids or proteins. In gram-negative bacteria there are generally two kinds of carbohydrate molecules covering the cell surface; lipopolysaccharides (or occasionally lipooligosaccharides) and capsular polysaccharides. Whilst the capsular polysaccharides, when present, are very long and loosely attached to the cell surface the lipopolysaccharides are anchored in the cell membrane and protrude perpendicular to it. Thus, in absence of a capsule, the surface presented to other microbes and the immune system is dominated by the ends of the lipopolysaccharide molecules. Here we show that structures presented to the environment are shared among a wide range of different bacteria and can often be predicted from the chemical structure of the polymer. Introduction The importance of lipopolysaccharides (LPS) for the survival of bacteria in their natural surrounding has long been recognised. There is however no consensus regarding their function in vivo and presumably they have several roles such as protection against bacteriophages, surface adhesion and resistance towards a variety of other environmental stresses [1]. Lipopolysaccharides are some of the most variable molecules produced by bacteria. The number of components in bacterial polysaccharides is staggering; a 1990 review counts 85 69 http://www.beilstein-institut.de/glycobioinf2011/Proceedings/Stenutz/Stenutz.pdf Cracking the Sugar Code by Navigating the Glycospace June 27 – July 1, 2011, Potsdam, Germany