Journal of Bacteriology, September 1998, p. 4872-4878, Vol. 180, No. 18
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Laboratoire d'Ingénierie des
Systèmes Macromoléculaires,
Received 9 March 1998/Accepted 7 July 1998
Mutations in the tol-pal genes induce pleiotropic
effects such as release of periplasmic proteins into the extracellular
medium and hypersensitivity to drugs and detergents. Other outer
membrane defective strains such as tolC, lpp,
and rfa mutations are also altered in their outer membrane
permeability. In this study, electron microscopy and Western blot
analyses were used to show that strains with mutations in each of the
tol-pal genes formed outer membrane vesicles after growth
in standard liquid or solid media. This phenotype was not observed in
tolC and rfaD cells in the same conditions. A
tolA deletion in three different Escherichia
coli strains was shown to lead to elevated amounts of vesicles.
These results, together with plasmid complementation experiments,
indicated that the formation of vesicles resulted from the defect of
any of the Tol-Pal proteins. The vesicles contained outer membrane trimeric porins correctly exposed at the cell surface. Pal outer membrane lipoprotein was also immunodetected in the vesicle fraction of
tol strains. The results are discussed in view of the role of the Tol-Pal transenvelope proteins in maintaining outer membrane integrity by contributing to target or integrate newly synthesized components of this structure.
*
Corresponding author. Mailing address: Laboratoire
d'Ingénierie des Systèmes Macromoléculaires, UPR
9027, CNRS, Institut de Biologie Structurale et Microbiologie 13402 Marseille Cedex 20, France. Phone: 33-4-91-76-03-59. Fax:
33-4-91-71-21-24. E-mail: lloubes{at}ibsm.cnrs-mrs.fr.
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