Biosynthesis of the O9 Antigen of <em>Escherichia coli</em>.

`The O9-specific mannan of Escherichia coil was synthesized in vitro from GDP-[14C]mannose by membranes which were obtained from a phosphomannose isomerase-less mutant of E. coli O9:K29- :H-, Subsequent treatment of the membranes with dilute acid liberated a neutral product, whereas with aqueous phenol a charged product was obtained. Chromatography on DEAE-cellulose, incubation with alkaline phosphatase and microdetermination showed that the charged mannan was substituted with one phosphate per chain. The neutral 14C-labelled product of the incubation hr vitro was reduced with sodium boro[&#179;H]hydride. After total acid hydrolysis, the radioactive material was chromatographed on paper in the presence of borate. It was found that [&#179;H]glucitol, but no [&#179;H, 14C]mannitol was present. When the neutral product, which was obtained after incubation of 14C-prelabelled membranes with nonradioactive GDP-mannose, was hydrolyzed with and without prior reduction with non-radioactive sodium borohydride, in subsequent paper chromatography, [14C]glucitol or [14C]glucose was found. The glucose was also converted enzymatically to gluconic acid, which was identified by paper electrophoresis. These results show that in the neutral O9-specific mannan glucose is at the reducing end and they indicate that the mannan chain grows at the non-reducing end. This is discussed with respect to the overall mechanism of the biosynthesis of the 09 antigen. [ABSTRACT FROM AUTHOR]