Functional Conservation of the Polysaccharide Biosynthetic Protein WbpM and Its Homologues in Pseudomonas aeruginosa and Other Medically Significant Bacteria

WbpM is a highly conserved protein involved in synthesis of the O antigens of Pseudomonas aeruginosa. Homologues of this protein have been identified in a large number of bacteria, and they can be divided into two subfamilies: subfamily 1, including WbpM, contains large proteins (∼600 amino acids), while subfamily 2, typified by HP0840 (FlaA1) of Helicobacter pylori, contains smaller proteins (∼350 amino acids) homologous to the C termini of proteins in subfamily 1. Analysis of knockout mutants of wbpM in P. aeruginosa serotypes O3, O10, O15, and O17 showed that although all 20 serotypes of P. aeruginosa possess wbpM, it is not universally required for O-antigen biosynthesis. Homologous genes from Bordetella pertussis (wlbL), Staphylococcus aureus (cap8D), and H. pylori (flaA1) complemented a P. aeruginosa O5 wbpM mutant to various degrees. These conserved proteins may represent interesting targets for the design of inhibitors of bacterial exopolysaccharide biosynthesis.