This Article Full Text Full Text (PDF) Supplemental material 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 Baek, S.-H. Articles by Shapleigh, J. P. Search for Related Content PubMed PubMed Citation Articles by Baek, S.-H. Articles by Shapleigh, J. P. Agricola Articles by Baek, S.-H. Articles by Shapleigh, J. P.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, August 2005, p. 4427-4436, Vol. 71, No. 8
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.8.4427-4436.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Expression of Nitrite and Nitric Oxide Reductases in Free-Living and Plant-Associated Agrobacterium tumefaciens C58 Cells

Seung-Hun Baek and James P. Shapleigh^*

Department of Microbiology, Wing Hall, Cornell University, Ithaca, New York 14853

Received 26 July 2004/ Accepted 23 February 2005

A number of the bacteria that form associations with plants are denitrifiers. To learn more about how the association with plants affects expression of denitrification genes, the regulation of nitrite and nitric oxide reductases was investigated in Agrobacterium tumefaciens. Analysis of free-living cells revealed that expression of the genes encoding nitrite and nitric oxide reductases, nirK and nor, respectively, requires low-oxygen conditions, nitric oxide, and the transcriptional regulator NnrR. Expression of nor was monitored in plant-associated bacteria using nor-gfp fusion expression. In root association experiments, only a small percentage of the attached cells were fluorescent, even when they were incubated under a nitrogen atmosphere. Inactivation of nirK had no significant effect on the ability of A. tumefaciens to bind to plant roots regardless of the oxygen tension, but it did decrease the occurrence of root-associated fluorescent cells. When wild-type cells containing the gfp fusion were infiltrated into leaves, most cells eventually became fluorescent. The same result was obtained when a nirK mutant was used, suggesting that nitric oxide activated nor expression in the endophytic bacteria. Addition of a nitric oxide synthase inhibitor to block nitric oxide generation by the plant prevented gfp expression in infiltrated nitrite reductase mutants, demonstrating that plant-derived nitric oxide can activate nor expression in infiltrated cells.

---

* Corresponding author. Mailing address: Department of Microbiology, Wing Hall, Cornell University, Ithaca, NY 14853. Phone: (607) 255-8535. Fax: (607) 255-3904. E-mail: jps2{at}cornell.edu.

Supplemental material for this article may be found at http://aem.asm.org/.

---

Applied and Environmental Microbiology, August 2005, p. 4427-4436, Vol. 71, No. 8
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.8.4427-4436.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Saleh-Lakha, S., Shannon, K. E., Goyer, C., Trevors, J. T., Zebarth, B. J., Burton, D. L. (2008). Nitric Oxide Reductase Gene Expression and Nitrous Oxide Production in Nitrate-Grown Pseudomonas mandelii. Appl. Environ. Microbiol. 74: 6876-6879 [Abstract] [Full Text]  
• Baek, S.-H., Hartsock, A., Shapleigh, J. P. (2008). Agrobacterium tumefaciens C58 Uses ActR and FnrN To Control nirK and nor Expression. J. Bacteriol. 190: 78-86 [Abstract] [Full Text]  
• Pothier, J. F., Wisniewski-Dye, F., Weiss-Gayet, M., Moenne-Loccoz, Y., Prigent-Combaret, C. (2007). Promoter-trap identification of wheat seed extract-induced genes in the plant-growth-promoting rhizobacterium Azospirillum brasilense Sp245. Microbiology 153: 3608-3622 [Abstract] [Full Text]