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Appl. Environ. Microbiol., Nov 1996, 4003-4008, Vol 62, No. 11
S Dukan, S Dadon, DR Smulski and S Belkin
A series of plasmids, containing fusions of different stress promoters to
lux reporter genes, was used in an attempt to monitor the defense circuits
activated upon exposure of Escherichia coli to sublethal doses of free
chlorine. A significant level of activation was exhibited by promoters of
three heat shock genes (grpE, dnaK, and lon), in an rpoH- dependent manner.
The promoter of micF, a gene under the control of the soxRS regulon, was
also strongly induced, but not in a soxR mutant. This induction was not
affected by sodA and sodB mutations, implying that it did not involve
oxygen radical activity. Free-chlorine activation of both heat shock and
soxRS regulons required an exposure of less then I s in duration. The oxyR
or the SOS regulons were apparently not induced by free chlorine (as judged
by lack of activation of katG and recA, respectively), and neither was the
universal stress (uspA) protein.
Copyright © 1996, American Society for Microbiology
Hypochlorous acid activates the heat shock and soxRS systems of Escherichia coli
J. Blaustein Desert Research Institute, Ben-Gurion University of the Negev, Israel. duk@ccr.jussieu.fr
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