Complex sentence: Lipooligosaccharide (LOS) is a low-weight version of lipopolysaccharide present on the surfaces of most other gram negative bacteria--it is a sugar side chain attached to a lipid, Lipid A, in the outer membrane coating the cell wall of the bacteria.
Split into simpler sentences: Lipooligosaccharide (LOS) is a low-weight version of lipopolysaccharide present on the surfaces of most other gram negative bacteria. It is a sugar (saccharide) side chain attached to a lipid (Lipid A thus "lipo -") in the outer membrane coating the cell wall of the bacteria.