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Periplasmic copper–zinc superoxide dismutase protects Haemophilus ducreyi from exogenous superoxide
Author(s) -
San Mateo Lani R.,
Hobbs Marcia M.,
Kawula Thomas H.
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.00687.x
Subject(s) - haemophilus ducreyi , periplasmic space , superoxide dismutase , biology , microbiology and biotechnology , superoxide , zinc , haemophilus , dismutase , biochemistry , bacteria , escherichia coli , pasteurellaceae , enzyme , haemophilus influenzae , chemistry , antibiotics , gene , genetics , organic chemistry
Haemophilus ducreyi causes chancroid, a sexually transmitted genital ulcer disease implicated in increased heterosexual transmission of HIV. As part of an effort to identify H . ducreyi gene products involved in virulence and pathogenesis, we created random Tn phoA insertion mutations in an H . ducreyi 35 000 library cloned in Escherichia coli . Inserts encoding exported or secreted PhoA fusion proteins were characterized by DNA sequencing. One such clone encoded a Cu–Zn superoxide dismutase (SOD) enzyme. The Cu–Zn SOD was periplasmic in H . ducreyi and accounted for most of the detectable SOD activity in whole‐cell lysates of H . ducreyi grown in vitro . To investigate the function of the Cu–Zn SOD, we created a Cu–Zn SOD‐deficient H . ducreyi strain by inserting a cat cassette into the sodC gene. The wild‐type and Cu–Zn SOD null mutant strains were equally resistant to excess cytoplasmic superoxide induced by paraquat, demonstrating that the Cu–Zn SOD did not function in the detoxification of cytoplasmic superoxide. However, the Cu–Zn SOD null strain was significantly more susceptible to killing by extracellular superoxide than the wild type. This result suggests that the H . ducreyi Cu–Zn SOD may play a role in bacterial defence against oxidative killing by host immune cells during infection.