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 Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by MacLean, A. M. Articles by Finan, T. M. Search for Related Content PubMed PubMed Citation Articles by MacLean, A. M. Articles by Finan, T. M. Agricola Articles by MacLean, A. M. Articles by Finan, T. M.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, August 2006, p. 5403-5413, Vol. 72, No. 8
0099-2240/06/$08.00+0     doi:10.1128/AEM.00580-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Characterization of the ß-Ketoadipate Pathway in Sinorhizobium meliloti

Allyson M. MacLean, Gordon MacPherson, Punita Aneja, and Turlough M. Finan^*

Center for Environmental Genomics, Department of Biology, McMaster University, Hamilton, Ontario, Canada

Received 10 March 2006/ Accepted 14 June 2006

Aromatic compounds represent an important source of energy for soil-dwelling organisms. The ß-ketoadipate pathway is a key metabolic pathway involved in the catabolism of the aromatic compounds protocatechuate and catechol, and here we show through enzymatic analysis and mutant analysis that genes required for growth and catabolism of protocatechuate in the soil-dwelling bacterium Sinorhizobium meliloti are organized on the pSymB megaplasmid in two transcriptional units designated pcaDCHGB and pcaIJF. The pcaD promoter was mapped by primer extension, and expression from this promoter is demonstrated to be regulated by the LysR-type protein PcaQ. ß-Ketoadipate succinyl-coenzyme A (CoA) transferase activity in S. meliloti was shown to be encoded by SMb20587 and SMb20588, and these genes have been renamed pcaI and pcaJ, respectively. These genes are organized in an operon with a putative ß-ketoadipyl-CoA thiolase gene (pcaF), and expression of the pcaIJF operon is shown to be regulated by an IclR-type transcriptional regulator, SMb20586, which we have named pcaR. We show that pcaR transcription is negatively autoregulated and that PcaR is a positive regulator of pcaIJF expression and is required for growth of S. meliloti on protocatechuate as the carbon source. The characterization of the protocatechuate catabolic pathway in S. meliloti offers an opportunity for comparison with related species, including Agrobacterium tumefaciens. Differences observed between S. meliloti and A. tumefaciens pcaIJ offer the first evidence of pca genes that may have been acquired after speciation in these closely related species.

---

* Corresponding author. Mailing address: Department of Biology, Life Sciences Building, McMaster University, 1020 Main St. West, Hamilton L8S 4K1, Ontario, Canada. Phone: (905) 525-9140, ext. 24000. Fax: (905) 628-6033. E-mail: finan{at}mcmaster.ca.

---

Applied and Environmental Microbiology, August 2006, p. 5403-5413, Vol. 72, No. 8
0099-2240/06/$08.00+0     doi:10.1128/AEM.00580-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Wattam, A. R., Williams, K. P., Snyder, E. E., Almeida, N. F. Jr., Shukla, M., Dickerman, A. W., Crasta, O. R., Kenyon, R., Lu, J., Shallom, J. M., Yoo, H., Ficht, T. A., Tsolis, R. M., Munk, C., Tapia, R., Han, C. S., Detter, J. C., Bruce, D., Brettin, T. S., Sobral, B. W., Boyle, S. M., Setubal, J. C. (2009). Analysis of Ten Brucella Genomes Reveals Evidence for Horizontal Gene Transfer Despite a Preferred Intracellular Lifestyle. J. Bacteriol. 191: 3569-3579 [Abstract] [Full Text]  
• MacLean, A. M., Anstey, M. I., Finan, T. M. (2008). Binding Site Determinants for the LysR-Type Transcriptional Regulator PcaQ in the Legume Endosymbiont Sinorhizobium meliloti. J. Bacteriol. 190: 1237-1246 [Abstract] [Full Text]