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Infection and Immunity, January 2000, p. 30-37, Vol. 68, No. 1
Department of Biology, Università di
Roma "Tor Vergata," 00133 Rome,1
Istituto Superiore di Sanità, 00161 Rome,3 and Istituto di Microbiologia, II
Università di Napoli, 80138 Naples,2
Italy, and Institut Jacques Monod, CNRS, Universités
Paris 6 and 7, Paris, France4
Received 2 August 1999/Returned for modification 10 September
1999/Accepted 21 October 1999
We have studied the influence of periplasmic Cu,Zn superoxide
dismutase on the intracellular survival of Escherichia coli strains able to invade epithelial cells by the expression of the inv gene from Yersinia pseudotuberculosis but
unable to multiply intracellularly. Intracellular viability assays,
confirmed by electron microscopy observations, showed that invasive
strains of E. coli engineered to increase Cu,Zn
superoxide dismutase production are much more resistant to
intracellular killing than strains containing only the chromosomal
sodC copy. However, we have found only a slight difference
in survival within HeLa cells between a sodC-null mutant
and its isogenic wild-type strain. Such a small difference in survival
correlates with the very low expression of this enzyme in the wild-type
strain. We have also observed that acid- and oxidative stress-sensitive
E. coli HB101(pRI203) is more rapidly killed in epithelial
cells than E. coli GC4468(pRI203). The high mortality of
E. coli HB101(pRI203), independent of the acidification of
the endosome, is abolished by the overexpression of sodC.
Our data suggest that oxyradicals are involved in the mechanisms of
bacterial killing within epithelial cells and that high-level
production of periplasmic Cu,Zn superoxide dismutase provides
bacteria with an effective protection against oxidative damage. We
propose that Cu,Zn superoxide dismutase could offer an
important selective advantage in survival within host cells to bacteria
expressing high levels of this enzyme.
0019-9567/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Increased Expression of Periplasmic Cu,Zn Superoxide
Dismutase Enhances Survival of Escherichia coli Invasive
Strains within Nonphagocytic Cells
*
Corresponding author. Mailing address: Department of
Biology, Università di Roma "Tor Vergata," Via della
Ricerca Scientifica, 00133 Rome, Italy. Phone: 39-0672594372. Fax: 39-0672594311. E-mail: andrea.battistoni{at}uniroma2.it.
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