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J. Bacteriol., 11 1995, 6330-6337, Vol 177, No. 22
DJ Hassett, HP Schweizer and DE Ohman
The consumption of molecular oxygen by Pseudomonas aeruginosa can lead to
the production of reduced oxygen species, including superoxide, hydrogen
peroxide, and the hydroxyl radical. As a first line of defense against
potentially toxic levels of endogenous superoxide, P. aeruginosa possesses
an iron- and manganese-cofactored superoxide dismutase (SOD) to limit the
damage evoked by this radical. In this study, we have generated mutants
which possess an interrupted sodA (encoding manganese SOD) or sodB
(encoding iron SOD) gene and a sodA sodB double mutant. Mutagenesis of sodA
did not significantly alter the aerobic growth rate in rich medium (Luria
broth) or in glucose minimal medium in comparison with that of wild-type
bacteria. In addition, total SOD activity in the sodA mutant was decreased
only 15% relative to that of wild-type bacteria. In contrast, sodB mutants
grew much more slowly than the sodA mutant or wild-type bacteria in both
media, and sodB mutants possessed only 13% of the SOD activity of wild-type
bacteria. There was also a progressive decrease in catalase activity in
each of the mutants, with the sodA sodB double mutant possessing only 40%
of the activity of wild-type bacteria. The sodA sodB double mutant grew
very slowly in rich medium and required approximately 48 h to attain
saturated growth in minimal medium. There was no difference in growth of
either strain under anaerobic conditions. Accordingly, the sodB but not the
sodA mutant demonstrated marked sensitivity to paraquat, a
superoxide-generating agent.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Pseudomonas aeruginosa sodA and sodB mutants defective in manganese- and iron-cofactored superoxide dismutase activity demonstrate the importance of the iron-cofactored form in aerobic metabolism
Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Ohio 45257-0524, USA.
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