Characterization of the Wzz proteins of P. aeruginosa serotype O13. (A) Gene deletions of wzz1 and wzz2 affect OSA chain length. The results indicate that Wzz1 regulates the long-chain OSA, while Wzz2 regulates the very-long-chain OSA in serotype O13. (B) Reciprocal swaps of the periplasmic and TM/cytosolic domains of Wzz1 and Wzz2. Lane 1, Wzz1; lane 2, Z2-Z1(prp)-Z2 (Wzz2 TM/cytosolic domains with Wzz1 periplasmic domain); lane 3, Wzz2; lane 4, Z1-Z2(prp)-Z1 (Wzz1 TM/cytosolic domains with Wzz2 periplasmic domain). (C) The constructs were expressed in the O13 Δwzz1 Δwzz2 double-mutant background. The results indicate that the periplasmic domain is the main determinant of chain length, while the TM/cytosolic regions play a minor role.