This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Jara, M. Articles by Barbé, J. Search for Related Content PubMed PubMed Citation Articles by Jara, M. Articles by Barbé, J.

Geobacter sulfurreducens Has Two Autoregulated lexA Genes Whose Products Do Not Bind the recA Promoter: Differing Responses of lexA and recA to DNA Damage

Department of Genetics and Microbiology, Universitat Autònoma de Barcelona,¹ Centre de Recerca en Sanitat Animal, Universitat Autònoma de Barcelona-Institut de Recerca i Tecnologia Agroalimentària, Bellaterra, 08193 Barcelona, Spain,⁴ Department of Microbiology, University of Massachusetts, Amherst, Massachusetts 01003,² Departamento de Microbiologia Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62251, Mexico³

Received 15 November 2002/ Accepted 23 January 2003

The Escherichia coli LexA protein was used as a query sequence in TBLASTN searches to identify the lexA gene of the -proteobacterium Geobacter sulfurreducens from its genome sequence. The results of the search indicated that G. sulfurreducens has two independent lexA genes designated lexA1 and lexA2. A copy of a dinB gene homologue, which in E. coli encodes DNA polymerase IV, is present downstream of each lexA gene. Reverse transcription-PCR analyses demonstrated that, in both cases, lexA and dinB constitute a single transcriptional unit. Electrophoretic mobility shift assays with purified LexA1 and LexA2 proteins have shown that both proteins bind the imperfect palindrome GGTTN₂CN₄GN₃ACC found in the promoter region of both lexA1 and lexA2. This sequence is also present upstream of the Geobacter metallireducens lexA gene, indicating that it is the LexA box of this bacterial genus. This palindrome is not found upstream of either the G. sulfurreducens or the G. metallireducens recA genes. Furthermore, DNA damage induces expression of the lexA-dinB transcriptional unit but not that of the recA gene. However, the basal level of recA gene expression is dramatically higher than that of the lexA gene. Likewise, the promoters of the G. sulfurreducens recN, ruvAB, ssb, umuDC, uvrA, and uvrB genes do not contain the LexA box and are not likely to bind to the LexA1 or LexA2 proteins. G. sulfurreducens is the first bacterial species harboring a lexA gene for which a constitutive expression of its recA gene has been described.

This article has been cited by other articles:

• da Rocha, R. P., de Miranda Paquola, A. C., do Valle Marques, M., Menck, C. F. M., Galhardo, R. S. (2008). Characterization of the SOS Regulon of Caulobacter crescentus. J. Bacteriol. 190: 1209-1218 [Abstract] [Full Text]  
• Abella, M., Campoy, S., Erill, I., Rojo, F., Barbe, J. (2007). Cohabitation of Two Different lexA Regulons in Pseudomonas putida. J. Bacteriol. 189: 8855-8862 [Abstract] [Full Text]  
• Hare, J. M., Perkins, S. N., Gregg-Jolly, L. A. (2006). A Constitutively Expressed, Truncated umuDC Operon Regulates the recA-Dependent DNA Damage Induction of a Gene in Acinetobacter baylyi Strain ADP1.. Appl. Environ. Microbiol. 72: 4036-4043 [Abstract] [Full Text]  
• Cune, J., Cullen, P., Mazon, G., Campoy, S., Adler, B., Barbe, J. (2005). The Leptospira interrogans lexA Gene Is Not Autoregulated. J. Bacteriol. 187: 5841-5845 [Abstract] [Full Text]  
• Campoy, S., Salvador, N., Cortes, P., Erill, I., Barbe, J. (2005). Expression of Canonical SOS Genes Is Not under LexA Repression in Bdellovibrio bacteriovorus. J. Bacteriol. 187: 5367-5375 [Abstract] [Full Text]  
• Yang, M.-K., Su, S.-R., Sung, V.-L. (2005). Identification and Characterization of a Second lexA Gene of Xanthomonas axonopodis Pathovar citri. Appl. Environ. Microbiol. 71: 3589-3598 [Abstract] [Full Text]  
• Nahrstedt, H., Schroder, C., Meinhardt, F. (2005). Evidence for two recA genes mediating DNA repair in Bacillus megaterium. Microbiology 151: 775-787 [Abstract] [Full Text]  
• Holmes, D. E., Nevin, K. P., Lovley, D. R. (2004). In Situ Expression of nifD in Geobacteraceae in Subsurface Sediments. Appl. Environ. Microbiol. 70: 7251-7259 [Abstract] [Full Text]