JB
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
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 HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Michiels, J.
Right arrow Articles by Vanderleyden, J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Michiels, J.
Right arrow Articles by Vanderleyden, J.

 Previous Article  |  Next Article 

J Bacteriol, April 1998, p. 1729-1740, Vol. 180, No. 7
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

The Rhizobium etli rpoN Locus: DNA Sequence Analysis and Phenotypical Characterization of rpoN, ptsN, and ptsA Mutants

Jan Michiels, Tom Van Soom, Inge D'hooghe, Bruno Dombrecht, Traki Benhassine,dagger Petra de Wilde, and Jos Vanderleyden*

F. A. Janssens Laboratory of Genetics, K. U. Leuven, B-3001 Heverlee, Belgium

Received 31 October 1997/Accepted 16 January 1998

The rpoN region of Rhizobium etli was isolated by using the Bradyrhizobium japonicum rpoN1 gene as a probe. Nucleotide sequence analysis of a 5,600-bp DNA fragment of this region revealed the presence of four complete open reading frames (ORFs), ORF258, rpoN, ORF191, and ptsN, coding for proteins of 258, 520, 191, and 154 amino acids, respectively. The gene product of ORF258 is homologous to members of the ATP-binding cassette-type permeases. ORF191 and ptsN are homologous to conserved ORFs found downstream from rpoN genes in other bacterial species. Unlike in most other microorganisms, rpoN and ORF191 are separated by approximately 1.6 kb. The R. etli rpoN gene was shown to control in free-living conditions the production of melanin, the activation of nifH, and the metabolism of C4-dicarboxylic acids and several nitrogen sources (ammonium, nitrate, alanine, and serine). Expression of the rpoN gene was negatively autoregulated and occurred independently of the nitrogen source. Inactivation of the ptsN gene resulted in a decrease of melanin synthesis and nifH expression. In a search for additional genes controlling the synthesis of melanin, an R. etli mutant carrying a Tn5 insertion in ptsA, a gene homologous to the Escherichia coli gene coding for enzyme I of the phosphoenolpyruvate:sugar phosphotransferase system, was obtained. The R. etli ptsA mutant also displayed reduced expression of nifH. The ptsN and ptsA mutants also displayed increased sensitivity to the toxic effects of malate and succinate. Growth of both mutants was inhibited by these C4-dicarboxylates at 20 mM at pH 7.0, while wild-type cells grow normally under these conditions. The effect of malate occurred independently of the nitrogen source used. Growth inhibition was decreased by lowering the pH of the growth medium. These results suggest that ptsN and ptsA are part of the same regulatory cascade, the inactivation of which renders the cells sensitive to toxic effects of elevated concentrations of malate or succinate.

* Corresponding author. Mailing address: F.A. Janssens Laboratory of Genetics, K.U. Leuven, Kardinaal Mercierlaan 92, B-3001 Heverlee, Belgium. Phone: 32 16 321631. Fax: 32 16 321966. E-mail: jozef.vanderleyden{at}agr.kuleuven.ac.be.

dagger Present address: Laboratoire de Biologie Moléculaire, Institut Pasteur d'Algérie, Alger, Algeria.




This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
Appl. Environ. Microbiol. Infect. Immun. Eukaryot. Cell
Mol. Cell. Biol. J. Virol. Microbiol. Mol. Biol. Rev.
ALL ASM JOURNALS

Copyright © 1998 by the American Society for Microbiology. All rights reserved.