Glucosylation of O-Antigen in Salmonella Carrying El5 and Es4 Phages*

Enzymatic reactions involved in the O-34 antigen formation of group E3 Salmonella carrying phages cl3 and ea4 was studied in vitro by the use of cells defective in UDP-glucose4-epimerase activity. Incorporation of glucose from UDPglucose into O-34 antigen required polymerization of mannosylrhamnosylgalactose repeating units. A single trisaccharide unit was not an acceptor for O-34 glucose. A preformed trisaccharide repeating polymer generated under restricted conditions was able to accept glucosyl residues. The product of glucose incorporation was characterized and found to be a haptenic 0-polysaccharide. A glucosyl-lipid intermediate was formed, which acted as a glucosyl donor to the polymeric trisaccharide units. Glucose incorporated into the intermediate in the first step reaction was transferred to the mannosylrhamnosylgalactose polymer generated in the second step. The following two enzymatic steps were formulated.