PslD is a secreted protein required for biofilm formation by Pseudomonas aeruginosa

Abstract

The function of pslD, which is part of the psl operon from Pseudomonas aeruginosa, was investigated in this study. The psl operon is involved in exopolysaccharide biosynthesis and biofilm formation. An isogenic marker-free pslD deletion mutant of P. aeruginosa PAO1 which was deficient in the formation of differentiated biofilms was generated. Expression of only the pslD gene coding region restored the wild-type phenotype. A C-terminal, hexahistidine tag fusion enabled the identification of PslD. LacZ and PhoA translational fusions with PslD indicated that PslD is a secreted protein required for biofilm formation, presumably via its role in exopolysaccharide export.

FIG. 1.

Fluorescence microscopy analysis of biofilms formed by P. aeruginosa after 3 days of growth in flow cell chambers. (A) P. aeruginosa PAO1. (B) P. aeruginosa PAO1ΔpslD. (C) P. aeruginosa PAO1ΔpslD(pBBR1-MCS5). (D) P. aeruginosa PAO1ΔpslD(pBBR1-MCS5::pslD).

FIG. 2.

Immunoblotting of whole-cell lysates of P. aeruginosa strains harboring various plasmids. Antihexahistidine antibodies were used to detect C-terminal, hexahistidine-tagged PslD. Lane 1, molecular mass standard of hexahistidine-tagged proteins; lane 2, P. aeruginosa PAO1; lane 3, P. aeruginosa PAO1ΔpslD(pBBR1-MCS5); and lane 4, P. aeruginosa PAO1ΔpslD(pBBR1-MCS5::HTpslD). The arrow indicates the position of C-terminal, hexahistidine-tagged PslD.