This Article Full Text Full Text (PDF) Other Versions of this Article: JB.00218-07v1 189/16/5955    most recent 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 Google Scholar Google Scholar Articles by Condemine, G. Articles by Ghazi, A. Search for Related Content PubMed PubMed Citation Articles by Condemine, G. Articles by Ghazi, A.

Differential Regulation of Two Oligogalacturonate Outer Membrane Channels, KdgN and KdgM, of Dickeya dadantii (Erwinia chrysanthemi)

Université de Lyon, F-69003 Lyon, Université Lyon 1, F-69622 Lyon, INSA-Lyon, F-69621 Villeurbanne, and CNRS UMR5240, Unité Microbiologie Adaptation et Pathogénie, F-69622 Lyon, France,¹ Groupe Canaux Ioniques, CNRS UMR8619, Université Paris-Sud, F-91405 Orsay, France²

Received 9 February 2007/ Accepted 6 June 2007

The entry of oligogalacturonates into Dickeya dadantii occurs through the specific channel KdgM. The genome of the bacterium encodes a second member of this family of outer membrane proteins, KdgN. We showed that this protein is also involved in the uptake of oligogalacturonates. When KdgN was reconstituted in proteoliposomes, it formed channels with a conductance of about 450 pS at a positive potential. These channels had weak anionic selectivity. The regulation of kdgN is complex, and five genes controlling the expression of kdgN have been identified: kdgR, pecS, ompR, hns, and crp. Moreover, kdgN was regulated by growth phase but only when bacteria were grown in rich medium. Most of these regulators of kdgN also control kdgM expression, but some of them regulate kdgM in the opposite manner: while PecS and OmpR are repressors of kdgM, they are activators of kdgN. This pattern resembles the regulation of the Escherichia coli general porins OmpF and OmpC, but such opposite regulation of two specific outer membrane channels has never been described before. KdgN may allow the bacteria to collect oligogalacturonates under saprophytic conditions, when virulence genes, including kdgM, are not expressed.

Published ahead of print on 15 June 2007.