ABSTRACTThe entry of oligogalacturonates intoDickeya dadantiioccurs 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 ofkdgNis complex, and five genes controlling the expression ofkdgNhave been identified:kdgR,pecS,ompR,hns, andcrp. Moreover,kdgNwas regulated by growth phase but only when bacteria were grown in rich medium. Most of these regulators ofkdgNalso controlkdgMexpression, but some of them regulatekdgMin the opposite manner: while PecS and OmpR are repressors ofkdgM, they are activators ofkdgN. This pattern resembles the regulation of theEscherichia coligeneral 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, includingkdgM, are not expressed.