Role of protein F in maintaining structural integrity of the Pseudomonas aeruginosa outer membrane.
To investigate the functional role of protein F of the outer membrane of Pseudomonas aeruginosa, we isolated mutants devoid of protein F, and the defective gene was transferred to a wild-type strain by plasmid FP5-mediated conjugation. Chemical analyses of the protein F-deficient outer membrane revealed that the amount of outer membrane protein was reduced to 72 to 74% of that of the protein F-sufficient strain and that lipopolysaccharides and phospholipids increased to 117 to 123% and 135 to 136%, respectively. The mutants and the transconjugant showed the following characteristics: (i) growth rates of protein F-deficient strains in low-osmolarity medium (e.g., L broth containing 0.1% NaCl) were less than 1/10 the rate of the protein F-sufficient strain; (ii) protein F-deficient cells were rounded, and the outer membrane formed large protruded blebs; and (iii) the outer membrane became physically fragile, since a significant amount of periplasmic proteins leaked out and the cells became highly sensitive to osmotic shock. The results suggested that protein F plays an important role in morphogenesis and in maintaining the integrity of the outer membrane. Determination of the diffusion rates of saccharides and beta-lactam antibiotics showed that the protein F-deficient outer membrane had no detectable transport defect compared with the protein F-sufficient outer membrane. The MICs of antibiotics for the protein F-deficient strains were nearly identical to those for the protein F-sufficient strain.
Gotoh
N
N
Department of Microbiology, Kyoto Pharmaceutical University, Japan.
Wakebe
H
H
Yoshihara
E
E
Nakae
T
T
Nishino
T
T
D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000502:physiology*; D002462:Cell Membrane / Q000648:ultrastructure*; D003227:Conjugation, Genetic; D005796:Genes; D005798:Genes, Bacterial; D008854:Microscopy, Electron; D009154:Mutation; D010957:Plasmids; D018272:Porins; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000648:ultrastructure*
D001425:Bacterial Outer Membrane Proteins; D018272:Porins