title: Mechanism of biological denitrification inhibition: procyanidins induce an allosteric transition of the membrane-bound nitrate reductase through membrane alteration.
abstract: Recently, it has been shown that procyanidins from Fallopia spp. inhibit bacterial denitrification, a phenomenon called biological denitrification inhibition (BDI). However, the mechanisms involved in such a process remain unknown. Here, we investigate the mechanisms of BDI involving procyanidins, using the model strain Pseudomonas brassicacearum NFM 421. The aerobic and anaerobic (denitrification) respiration, cell permeability and cell viability of P. brassicacearum were determined as a function of procyanidin concentration. The effect of procyanidins on the bacterial membrane was observed using transmission electronic microscopy. Bacterial growth, denitrification, NO3- and NO2-reductase activity, and the expression of subunits of NO3- (encoded by the gene narG) and NO2-reductase (encoded by the gene nirS) under NO3 or NO2 were measured with and without procyanidins. Procyanidins inhibited the denitrification process without affecting aerobic respiration at low concentrations. Procyanidins also disturbed cell membranes without affecting cell viability. They specifically inhibited NO3- but not NO2-reductase.Pseudomonas brassicacearum responded to procyanidins by over-expression of the membrane-bound NO3-reductase subunit (encoded by the gene narG). Our results suggest that procyanidins can specifically inhibit membrane-bound NO3-reductase inducing enzymatic conformational changes through membrane disturbance and that P. brassicacearum responds by over-expressing membrane-bound NO3-reductase. Our results lead the way to a better understanding of BDI.
authors.affiliation: Université de Lyon, UMR 5557 LEM, Université Lyon 1, CNRS, INRA USC 1364, F-69622 Villeurbanne Cedex, France Université de Lyon, UMR5023 LEHNA, Université Lyon 1, CNRS, ENTPE, F-69622 Villeurbanne Cedex, France clementbardon@hotmail.fr.
authors.forename: Clément
authors.initials: C
authors.lastname: Bardon
authors.affiliation: Université de Lyon, UMR 5557 LEM, Université Lyon 1, CNRS, INRA USC 1364, F-69622 Villeurbanne Cedex, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Poly
authors.affiliation: Université de Lyon, UMR5023 LEHNA, Université Lyon 1, CNRS, ENTPE, F-69622 Villeurbanne Cedex, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Piola
authors.affiliation: Université de Lyon, UMR5276 LGLTPE, Université Lyon 1, CNRS, ENTPE, F-69622 Villeurbanne Cedex, France.
authors.forename: Muriel
authors.initials: M
authors.lastname: Pancton
authors.affiliation: Université de Lyon, UMR 5557 LEM, Université Lyon 1, CNRS, INRA USC 1364, F-69622 Villeurbanne Cedex, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Comte
authors.affiliation: Université de Lyon, UMR 5557 LEM, Université Lyon 1, CNRS, INRA USC 1364, F-69622 Villeurbanne Cedex, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Meiffren
authors.affiliation: Université de Lyon, UMR 5557 LEM, Université Lyon 1, CNRS, INRA USC 1364, F-69622 Villeurbanne Cedex, France.
authors.forename: Feth el Zahar
authors.initials: Fel Z
authors.lastname: Haichar
mesh_terms: D000494:Allosteric Regulation; D044946:Biflavonoids; D002392:Catechin; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D058440:Denitrification; D000069263:Fallopia / Q000378:metabolism* / Q000382:microbiology*; D050901:Nitrate Reductase / Q000737:chemistry / Q000378:metabolism*; D009566:Nitrates / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics; D044945:Proanthocyanidins / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology* / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D044946:Biflavonoids; D009566:Nitrates; D044945:Proanthocyanidins; C017674:procyanidin; D002392:Catechin; D010088:Oxidoreductases; D050901:Nitrate Reductase
keywords: allosteric transition; biological denitrification inhibition; membrane alteration; membrane-bound enzyme; nitrate reductase; procyanidins