This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplemental material
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Blancato, V. S.
Right arrow Articles by Magni, C.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Blancato, V. S.
Right arrow Articles by Magni, C.

 Previous Article  |  Next Article 

Journal of Bacteriology, November 2008, p. 7419-7430, Vol. 190, No. 22
0021-9193/08/$08.00+0     doi:10.1128/JB.01704-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Transcriptional Regulation of the Citrate Gene Cluster of Enterococcus faecalis Involves the GntR Family Transcriptional Activator CitO{triangledown} ,{dagger}

Víctor S. Blancato, Guillermo D. Repizo, Cristian A. Suárez, and Christian Magni*

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina

Received 23 October 2007/ Accepted 7 September 2008

The genome of the gram-positive bacterium Enterococcus faecalis contains the genes that encode the citrate lyase complex. This complex splits citrate into oxaloacetate and acetate and is involved in all the known anaerobic bacterial citrate fermentation pathways. Although citrate fermentation in E. faecalis has been investigated before, the regulation and transcriptional pattern of the cit locus has still not been fully explored. To fill this gap, in this paper we demonstrate that the GntR transcriptional regulator CitO is a novel positive regulator involved in the expression of the cit operons. The transcriptional analysis of the cit clusters revealed two divergent operons: citHO, which codes for the transporter (citH) and the regulatory protein (citO), and upstream from it and in the opposite direction the oadHDB-citCDEFX-oadA-citMG operon, which includes the citrate lyase subunits (citD, citE, and citF), the soluble oxaloacetate decarboxylase (citM), and also the genes encoding a putative oxaloacetate decarboxylase complex (oadB, oadA, oadD and oadH). This analysis also showed that both operons are specifically activated by the addition of citrate to the medium. In order to study the functional role of CitO, a mutant strain with an interrupted citO gene was constructed, causing a total loss of the ability to degrade citrate. Reintroduction of a functional copy of citO to the citO-deficient strain restored the response to citrate and the Cit+ phenotype. Furthermore, we present evidence that CitO binds to the cis-acting sequences O1 and O2, located in the cit intergenic region, increasing its affinity for these binding sites when citrate is present and allowing the induction of both cit promoters.

* Corresponding author. Mailing address: Departamento de Microbiología, Suipacha 531, S2002LRK Rosario, Argentina. Phone: 54 341 435 0661. Fax: 54 341 439 0465. E-mail: chmagni{at}infovia.com.ar

{triangledown} Published ahead of print on 19 September 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, November 2008, p. 7419-7430, Vol. 190, No. 22
0021-9193/08/$08.00+0     doi:10.1128/JB.01704-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





Copyright © 2009 by the American Society for Microbiology.   For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»