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Journal of Bacteriology, June 2001, p. 3399-3407, Vol. 183, No. 11
Department of Molecular Biology and
Immunology, University of North Texas Health Science Center at Fort
Worth, Fort Worth, Texas 76107-2699
Received 19 January 2001/Accepted 21 March 2001
A gene encoding superoxide dismutase (SOD), sodM, from
S. aureus was cloned and characterized. The deduced amino
acid sequence specifies a 187-amino-acid protein with 75% identity to
the S. aureus SodA protein. Amino acid sequence comparisons
with known SODs and relative insensitivity to hydrogen peroxide and
potassium cyanide indicate that SodM most likely uses manganese (Mn) as a cofactor. The sodM gene expressed from a plasmid rescued
an Escherichia coli double mutant (sodA sodB)
under conditions that are otherwise lethal. SOD activity gels of
S. aureus RN6390 whole-cell lysates revealed three closely
migrating bands of activity. The two upper bands were absent in a
sodM mutant, while the two lower bands were absent in a
sodA mutant. Thus, the middle band of activity most likely
represents a SodM-SodA hybrid protein. All three bands of activity
increased as highly aerated cultures entered the late exponential phase
of growth, SodM more so than SodA. Viability of the sodA
and sodM sodA mutants but not the sodM mutant
was drastically reduced under oxidative stress conditions generated by
methyl viologen (MV) added during the early exponential phase of
growth. However, only the viability of the sodM sodA mutant was reduced when MV was added during the late exponential and stationary phases of growth. These data indicate that while SodA may be
the major SOD activity in S. aureus throughout all stages of growth, SodM, under oxidative stress, becomes a major source of
activity during the late exponential and stationary phases of growth
such that viability and growth of an S. aureus sodA mutant
are maintained.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.11.3399-3407.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Identification and Characterization of a Second
Superoxide Dismutase Gene (sodM) from
Staphylococcus aureus
*
Corresponding author. Mailing address: Department of
Molecular Biology and Immunology, University of North Texas Health
Science Center at Fort Worth, 3500 Camp Bowie Blvd., Fort Worth, TX
76107-2699. Phone: (817) 735-2110. Fax: (817) 735-2118. E-mail:
mhart{at}hsc.unt.edu.
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