title: Ecosystem screening approach for pathogen-associated microorganisms affecting host disease.
abstract: The microbial community in which a pathogen evolves is fundamental to disease outcome. Species interacting with a pathogen on the host surface shape the distribution, density, and genetic diversity of the inoculum, but the role of these species is rarely determined. The screening method developed here can be used to characterize pathogen-associated species affecting disease. This strategy involves three steps: (i) constitution of the microbial community, using the pathogen as a trap; (ii) community selection, using extracts from the pathogen as the sole nutrient source; and (iii) molecular identification and the screening of isolates focusing on their effects on the growth of the pathogen in vitro and host disease. This approach was applied to a soilborne plant pathogen, Phytophthora parasitica, structured in a biofilm, for screening the microbial community from the rhizosphere of Nicotiana tabacum (the host). Two of the characterized eukaryotes interfered with the oomycete cycle and may affect the host disease. A Vorticella species acted through a mutualistic interaction with P. parasitica, disseminating pathogenic material by leaving the biofilm. A Phoma species established an amensal interaction with P. parasitica, strongly suppressing disease by inhibiting P. parasitica germination. This screening method is appropriate for all nonobligate pathogens. It allows the definition of microbial species as promoters or suppressors of a disease for a given biotope. It should also help to identify important microbial relationships for ecology and evolution of pathogens.
authors: Institut National de la Recherche Agronomique, Unité Mixte de Recherche 1301 Interactions Biotiques et Santé Végétale, F-06903 Sophia Antipolis, France. galiana@sophia.inra.fr
authors: Eric
authors: E
authors: Galiana
authors: Antoine
authors: A
authors: Marais
authors: Catherine
authors: C
authors: Mura
authors: Benoît
authors: B
authors: Industri
authors: Gilles
authors: G
authors: Arbiol
authors: Michel
authors: M
authors: Ponchet
mesh_terms: D001203:Ascomycota / Q000254:growth & development*; D018441:Biofilms / Q000254:growth & development; D017753:Ecosystem; D056265:Microbial Interactions; D008969:Molecular Sequence Data; D016802:Oligohymenophorea / Q000254:growth & development*; D010838:Phytophthora / Q000254:growth & development* / Q000472:pathogenicity; D010935:Plant Diseases / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology; D058441:Rhizosphere; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D014026:Nicotiana / Q000382:microbiology*