title: Bactericidal Compounds Controlling Growth of the Plant Pathogen Pseudomonas syringae pv. actinidiae, Which Forms Biofilms Composed of a Novel Exopolysaccharide.
abstract: Pseudomonas syringae pv. actinidiae is the major cause of bacterial canker and is a severe threat to kiwifruit production worldwide. Many aspects of the disease caused by P. syringae pv. actinidiae, such as the pathogenicity-relevant formation of a biofilm composed of extracellular polymeric substances (EPSs), are still unknown. Here, a highly virulent strain of P. syringae pv. actinidiae, NZ V-13, was studied with respect to biofilm formation and architecture using a flow cell system combined with confocal laser scanning microscopy. The biofilm formed by P. syringae pv. actinidiae NZ V-13 was heterogeneous, consisting of a thin cellular base layer 5 μm thick and microcolonies with irregular structures. The major component of the EPSs produced by P. syringae pv. actinidiae NZ V-13 bacteria was isolated and identified to be an exopolysaccharide. Extensive compositional and structural analysis showed that rhamnose, fucose, and glucose were the major constituents, present at a ratio of 5:1.5:2. Experimental evidence that P. syringae pv. actinidiae NZ V-13 produces two polysaccharides, a branched α-d-rhamnan with side chains of terminal α-d-Fucf and an α-d-1,4-linked glucan, was obtained. The susceptibility of the cells in biofilms to kasugamycin and chlorine dioxide was assessed. About 64 and 73% of P. syringae pv. actinidiae NZ V-13 cells in biofilms were killed when kasugamycin and chlorine dioxide were used at 5 and 10 ppm, respectively. Kasugamycin inhibited the attachment of P. syringae pv. actinidiae NZ V-13 to solid surfaces at concentrations of 80 and 100 ppm. Kasugamycin was bacteriostatic against P. syringae pv. actinidiae NZ V-13 growth in the planktonic mode, with the MIC being 40 to 60 ppm and a bactericidal effect being found at 100 ppm. Here we studied the formation, architecture, and composition of P. syringae pv. actinidiae biofilms as well as used the biofilm as a model to assess the efficacies of bactericidal compounds.
authors.affiliation: Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
authors.forename: Shirin
authors.initials: S
authors.lastname: Ghods
authors.affiliation: The Ferrier Research Institute, Victoria University of Wellington, Petone, New Zealand.
authors.forename: Ian M
authors.initials: IM
authors.lastname: Sims
authors.affiliation: Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
authors.forename: M Fata
authors.initials: MF
authors.lastname: Moradali
authors.affiliation: Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand B.Rehm@massey.ac.nz.
authors.forename: Bernd H A
authors.initials: BH
authors.lastname: Rehm
mesh_terms: D029042:Actinidia / Q000382:microbiology; D000617:Aminoglycosides / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D017606:Chlorine Compounds / Q000494:pharmacology*; D005638:Fruit / Q000382:microbiology; D008826:Microbial Sensitivity Tests; D010087:Oxides / Q000494:pharmacology*; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D044224:Pseudomonas syringae / Q000187:drug effects* / Q000254:growth & development
chemical_list: D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D017606:Chlorine Compounds; D010087:Oxides; D011135:Polysaccharides, Bacterial; C064841:exopolysaccharide, Pseudomonas; C025109:chlorine dioxide; C100305:kasugamycin
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