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J. Bacteriol., Sep 1995, 5254-5260, Vol 177, No. 18
JW Sanders, KJ Leenhouts, AJ Haandrikman, G Venema and J Kok
In an analysis of the stress response of Lactococcus lactis, three proteins
that were induced under low pH culture conditions were detected. One of
these was identified as the lactococcal superoxide dismutase (SodA) by
N-terminal amino acid sequence analysis. The gene encoding this protein,
designated sodA, was cloned by the complementation of a sodA sodB
Escherichia coli strain. The deduced amino acid sequence of L. lactis SodA
showed the highest degree of similarity to the manganese-containing Sod
(MnSod) of Bacillus stearothermophilus. A promoter upstream of the sodA
gene was identified by primer extension analysis, and an inverted repeat
surrounding the - 35 hexanucleotide of this promoter is possibly involved
in the regulation of the expression of sodA. The expression of sodA was
analyzed by transcriptional fusions with a promoterless lacZ gene. The
induction of beta-galactosidase activity occurred in aerated cultures.
Deletion experiments revealed that a DNA fragment of more than 130 bp
surrounding the promoter was needed for the induction of lacZ expression by
aeration. The growth rate of an insertion mutant of sodA did not differ
from that of the wild type in standing cultures but was decreased in
aerated cultures.
Copyright © 1995, American Society for Microbiology
Stress response in Lactococcus lactis: cloning, expression analysis, and mutation of the lactococcal superoxide dismutase gene
Department of Genetics, University of Groningen, NN Haren, The Netherlands.
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