Biosynthesis of the O antigen from Citrobacter 139.

The biosynthesis of the O antigen of Citrobacter 139 (Escherichia coli 3 Zurich 4,5,12:z(20)) was shown to proceed through a series of lipid-linked intermediates, similar to those involved in O-antigen synthesis in Salmonella. Galactose was the first sugar incorporated, followed by rhamnose and mannose. Abequose was incorporated from cytidine diphosphate (CDP)-abequose only when all three of the other nucleotide sugars (uridine diphosphate galactose, guanosine diphosphate mannose, and thymidine diphosphate rhamnose) were present. Rhamnosyl-galactosyl 1-phosphate and mannosyl-rhamnosyl-galactosyl 1-phosphate were identified as the products of mild alkaline hydrolysis of the lipid-linked intermediates.