Characterization of the serogroup O11O-antigen locus of Pseudomonas aeruginosa PA103

We previously cloned a genomic DNA fragment from the serogroup O11 Pseudomo nas aeruginosa strain PA103 that contained all genes necessary for O-antige n synthesis and directed the expression of serogroup O11 antigen on recombi nant Escherichia coli and Salmonella. To elucidate the pathway of serogroup O11 antigen synthesis, the nucleotide sequence of the biosynthetic genes w as determined. Eleven open reading frames likely to be involved in serogrou p O11 O-antigen biosynthesis were identified and are designated in order as wzz(PaO111) (wzz from P. aeruginosa serogroup O11), wzx(PaO11), wbjA, wzy( PaO11), wbjB to wbjF, wbpL(O11) and wbpM(O11) (wbpL and wbpM from serogroup O11), Consistent with previous descriptions of O-antigen biosynthetic gene loci, the entire region,vith the exception of wbpM(O11) has a markedly red uced G + C content relative to the chromosomal average. Wzy(PaO11) shows no significant similarity at the protein or DNA sequence level to any databas e sequence and is very hydrophobic, with 10 to 12 putative transmembrane do mains, both typical characteristics of O-antigen polymerases. A nonpolar ch romosomal insertion mutation in wzy(PaO11) in P. aeruginosa PA103 confirmed the identity of this gene. There is striking similarity between WbjBCDE an d Cap(5/8)EFGL, involved in type 5 and type 8 capsule biosynthesis in Staph ylococcus aureus. There is nearly total identity between wbpM(O11) and wbpM (O5), previously shown by others to be present in all 20 P. aeruginosa sero groups. Using similarity searches, we have assigned functions to the protei ns encoded by the PA103 O-antigen locus and present the potential steps in the pathway for the biosynthesis of P. aeruginosa serogroup O11 O antigen.