2002. Relationship of Yersinia pseudotuberculosis O

O antigen is part of the lipopolysaccharide present in the outer membrane of gram-negative bacteria and is highly polymorphic. In this study, we obtained sequences of the O-antigen gene clusters for the Yersinia pseudotuberculosis antigens IA, IIA, and IVB. We propose that the IIA gene cluster was derived from the IVB cluster, one of the very few cases in which a parent gene cluster is identified, and that the IA gene cluster could be a hybrid of the IVB and IB gene clusters. All three O antigens contain 6-deoxy-D-mannoheptose, and we identified six genes for the biosynthetic pathway for the precursor of this sugar, GDP-6-deoxy-D-mannoheptose. Lipopolysaccharide (LPS), an important component of the outer membrane of gram-negative bacteria, usually consists of three distinct regions: lipid A, core oligosaccharide, and O-specific polysaccharide (O antigen). The O antigen consists of repeats of an O unit of generally two to six sugars, and in most species it is highly polymorphic, with many forms that can vary in the types of sugars present, in their relative arrangement within the repeat unit, and in the linkage between repeat units (12). The genes for O-antigen synthesis are normally groupe