TheHelicobacter pylori flaA1andwbpBGenes Control Lipopolysaccharide and Flagellum Synthesis and Function

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Abstract
flaA1andwbpBare conserved genes with unknown biological function inHelicobacter pylori.Since both genes are predicted to be involved in lipopolysaccharide (LPS) biosynthesis, flagellum assembly, or protein glycosylation, they could play an important role in the pathogenesis ofH. pylori.To determine their biological role, both genes were disrupted in strain NCTC 11637. Both mutants exhibited altered LPS, with loss of most O-antigen and core modification, and increased sensitivity to sodium dodecyl sulfate compared to wild-type bacteria. These defects could be complemented in a gene-specific manner. Also,flaA1could complement these defects in thewbpBmutant, suggesting a potential redundancy of the reductase activity encoded by both genes. Both mutants were nonmotile, although thewbpBmutant still produced flagella. The defect in the flagellum functionality of this mutant was not due to a defect in flagellin glycosylation since flagellins from wild-type strain NCTC 11637 were shown not to be glycosylated. TheflaA1mutant produced flagellins but no flagellum. Overall, the similar phenotypes observed for both mutants and the complementation of thewbpBmutant byflaA1suggest that both genes belong to the same biosynthesis pathway. The data also suggest thatflaA1andwbpBare at the interface between several pathways that govern the expression of different virulence factors. We propose that FlaA1 and WbpB synthesize sugar derivatives dedicated to the glycosylation of proteins which are involved in LPS and flagellum production and that glycosylation regulates the activity of these proteins.