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J. Bacteriol., Apr 1996, 2131-2135, Vol 178, No. 7
JA Chesney, JW Eaton and JR Mahoney Jr
Aerobic organisms possess a number of often overlapping and well-
characterized defenses against common oxidants such as superoxide and
hydrogen peroxide. However, much less is known of mechanisms of defense
against halogens such as chlorine compounds. Although chlorine-based
oxidants may oxidize a number of cellular components, sulfhydrl groups are
particularly reactive. We have, therefore, assessed the importance of
intracellular glutathione in protection of Escherichia coli cells against
hydrogen peroxide, hypochlorous acid, and chloramines. Employing a
glutathione-deficient E. coli strain (JTG10) and an otherwise isogenic
glutathione-sufficient E. coli strain (AB1157), we find that
glutathione-deficient organisms are approximately twice as sensitive to
killing by both hydrogen peroxide and chlorine compounds. However, the mode
of protection by glutathione in these two cases appears to differ:
exogenous glutathione added to glutathione-deficient E. coli in amounts
equal to those which would be present in a similar suspension of the
wild-type bacteria fully restored resistance of glutathione-deficient
bacteria to chlorine-based oxidants but did not change resistance to
hydrogen peroxide. Furthermore, in protection against chlorine compounds,
oxidized glutathione is almost as effective as reduced glutathione,
implying that the tripeptide and/or oxidized thiol undergo further
reactions with chlorine compounds. Indeed, in vitro, 1 mol of reduced
glutathione will react with approximately 3.5 to 4.0 mol of hypochlorous
acid. We conclude that glutathione defends E. coli cells against attack by
chlorine compounds and hydrogen peroxide but, in the case of the halogen
compounds, does so nonenzymatically and sacrificially.
Copyright © 1996, American Society for Microbiology
Bacterial glutathione: a sacrificial defense against chlorine compounds
Picower Institute, Manhassett, New York 11030, USA.
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