Isolation and characterization of Escherichia coli mutants blocked in production of membrane-derived oligosaccharides.

We report a new procedure for the facile selection of mutants of Escherichia coli that are blocked in the production of membrane-derived oligosaccharides. Four phenotypic classes were identified, including two with a novel array of characteristics. The mutations mapped to two genetic loci. Mutations in the mdoA region near 23 min are in two distinct genes, only one of which is needed for the membrane-localized glucosyltransferase that catalyzes the synthesis of the beta-1,2-glucan backbone of membrane-derived oligosaccharides. Another set of mutations mapped near 27 min closely linked to osmZ; these appear to be in the galU gene.