LAUSR

Many genes in the biosynthetic pathway of lipopolysaccharide in C. sakazakii have not been identified. In this study, we demonstrate that an operon containing four genes ESA_RS18945, ESA_RS18950, ESA_RS18955, and ESA_RS18960 is responsible for L-glycero-D-mannoheptose addition on the inner core of lipopolysaccharide in C. sakazakii. The proteins encoded by these four genes are homologous to E. coli WaaQ, WaaC, WaaF, and WaaD. Lipopolysaccharide from the deletion mutants of ESA_RS18945, ESA_RS18950, ESA_RS18955, and ESA_RS18960 (named as △RS18945, △RS18950, △RS18955 and △RS18960, respectively) were analyzed by SDS-PAGE. △RS18945 synthesized lipopolysaccharide with similar length to the wild type BAA-894, whereas △RS18950, △RS18955 and △RS18960 synthesized much shorter lipopolysaccharide. This suggests that the enzyme encoded by ESA_RS18945 might function as E. coli WaaQ on the side chain of lipopolysaccharide. When E. coli WaaC, WaaF, and WaaD were overexpressed in △RS18950, △RS18955 and △RS18960, respectively, the full length of lipopolysaccharide was recovered. Mass spectrometry analysis indicates that △RS18950 and △RS18960 only synthesized Kdo2 -lipid A, confirming that enzymes encoded by ESA_RS18950 and ESA_RS18960 have similar functions to E. coli WaaC and WaaD, respectively. Hep-Kdo2 -lipid A with a phosphoethanolamine was produced in △RS18955, suggesting that the enzyme encoded by ESA_RS18955 has similar function to E. coli WaaF. This article is protected by copyright. All rights reserved.