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Journal of Bacteriology, November 1998, p. 5769-5775, Vol. 180, No. 21
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

Yi-Ywan M. Chen,1,2 Cheryl A. Weaver,1 David R. Mendelsohn,1 and Robert A. Burne1,2,*

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 sigma 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 (PureIDelta 100), and a promoterless chloramphenicol acetyltransferase (CAT) gene were constructed and integrated into the chromosome to generate strains PureICAT and PureIDelta 100CAT, respectively. CAT specific activities of PureICAT were repressed at pH 7.0 and induced at pH 5.5 and by excess carbohydrate. In PureIDelta 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.

Journal of Bacteriology, November 1998, p. 5769-5775, Vol. 180, No. 21
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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