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Journal of Bacteriology, December 2001, p. 7260-7272, Vol. 183, No. 24
Department of Molecular Microbiology and
Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv
University, Ramat Aviv, Israel
Received 3 July 2001/Accepted 19 September 2001
Staphylococcus aureus is a gram-positive facultative
aerobe that can grow in the absence of oxygen by fermentation or by
using an alternative electron acceptor. To investigate the mechanism by
which S. aureus is able to adapt to changes in oxygen
concentration, we analyzed the transcriptional regulation of genes that
encode the aerobic class Ib and anaerobic class III ribonucleotide
reductase (RNR) systems that are responsible for the synthesis of
deoxyribonucleotides needed for DNA synthesis. The S.
aureus class Ib RNR nrdIEF and class III RNR
nrdDG genes and their regulatory regions were cloned and
sequenced. Inactivation of the nrdDG genes showed that
the class III RNR is essential for anaerobic growth. Inhibition of aerobic growth by hydroxyurea showed that the class Ib RNR is an
oxygen-dependent enzyme. Northern blot analysis and primer extension
analysis demonstrated that transcription of class III nrdDG genes is regulated by oxygen concentration and was
at least 10-fold higher under anaerobic than under aerobic conditions. In contrast, no significant effect of oxygen concentration was found on
the transcription of class Ib nrdIEF genes. Disruption or deletion of S. aureus nrdDG genes caused up to a
fivefold increase in nrdDG and nrdIEF
transcription under anaerobic conditions but not under aerobic
conditions. Similarly, hydroxyurea, an inhibitor of the class I RNRs,
resulted in increased transcription of class Ib and class III RNR genes
under aerobic conditions. These findings establish that transcription
of class Ib and class III RNR genes is upregulated under conditions
that cause the depletion of deoxyribonucleotide. Promoter analysis of
class Ib and class III RNR operons identified several inverted-repeat
elements that may account for the transcriptional response of the
nrdIEF and nrdDG genes to oxygen.
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.24.7260-7272.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Analysis of Transcription of the
Staphylococcus aureus Aerobic Class Ib and Anaerobic
Class III Ribonucleotide Reductase Genes in Response to
Oxygen
*
Corresponding author. Mailing address: Department of
Molecular Microbiology and Biotechnology, George S. Wise Faculty of
Life Sciences, Tel Aviv University, Ramat Aviv, Israel, 69978. Phone: (972) 3 6409649. Fax: (972) 3 6409407. E-mail:
coheng{at}post.tau.ac.il.
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