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Journal of Bacteriology, November 1998, p. 5769-5775, Vol. 180, No. 21
Center for Oral
Biology1 and
Department of Microbiology
and Immunology,2 School of Medicine and
Dentistry, University of Rochester, Rochester, New York 14642
Received 29 May 1998/Accepted 26 August 1998
The Streptococcus salivarius 57.I ure
cluster was organized as an operon, beginning with
ureI, followed by ureABC (structural genes) and
ureEFGD (accessory genes). Northern analyses revealed transcripts encompassing structural genes and transcripts containing the entire operon. A
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Transcriptional Regulation of the
Streptococcus salivarius 57.I Urease Operon
70-like promoter could be
mapped 5' to ureI (PureI) by primer extension analysis. The intensity of the signal increased when cells were grown
at an acidic pH and was further enhanced by excess carbohydrate. To
determine the function(s) of two inverted repeats located 5' to
PureI, transcriptional fusions of the full-length promoter region (PureI), or a deletion derivative
(PureI
100), and a promoterless chloramphenicol
acetyltransferase (CAT) gene were constructed and integrated into the
chromosome to generate strains PureICAT and
PureI
100CAT, respectively. CAT specific activities of
PureICAT were repressed at pH 7.0 and induced at pH 5.5 and
by excess carbohydrate. In PureI
100CAT, CAT activity was
60-fold higher than in PureICAT at pH 7.0 and pH induction
was nearly eliminated, indicating that expression was negatively
regulated. Thus, it was concluded that PureI was the
predominant, regulated promoter and that regulation was governed by a
mechanism differing markedly from other known mechanisms for bacterial
urease expression.
*
Corresponding author. Mailing address: Center for Oral
Biology, University of Rochester, School of Medicine and Dentistry, 601 Elmwood Ave., Rochester, NY 14642. Phone: (716) 275-0381. Fax: (716)
473-2679. E-mail: robert_burne{at}urmc.rochester.edu.
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