title: Confocal microscopy reveals in planta dynamic interactions between pathogenic, avirulent and non-pathogenic Pseudomonas syringae strains.
abstract: Recent advances in genomics and single-cell analysis have demonstrated the extraordinary complexity reached by microbial populations within their hosts. Communities range from complex multispecies groups to homogeneous populations differentiating into lineages through genetic or non-genetic mechanisms. Diversity within bacterial populations is recognized as a key driver of the evolution of animal pathogens. In plants, however, little is known about how interactions between different pathogenic and non-pathogenic variants within the host impact on defence responses, or how the presence within a mixture may affect the development or the fate of each variant. Using confocal fluorescence microscopy, we analysed the colonization of the plant apoplast by individual virulence variants of Pseudomonas syringae within mixed populations. We found that non-pathogenic variants can proliferate and even spread beyond the inoculated area to neighbouring tissues when in close proximity to pathogenic bacteria. The high bacterial concentrations reached at natural entry points promote such interactions during the infection process. We also found that a diversity of interactions take place at a cellular level between virulent and avirulent variants, ranging from dominant negative effects on proliferation of virulent bacteria to in trans suppression of defences triggered by avirulent bacteria. Our results illustrate the spatial dynamics and complexity of the interactions found within mixed infections, and their potential impact on pathogen evolution.
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterranea "La Mayora", Universidad de Malaga-Consejo Superior de Investigaciones Cientificas (IHSM-UMA-CSIC), Departamento Biologia Celular, Genetica y Fisiologia, Campus de Teatinos, Malaga E-29071, Spain.
authors.forename: José S
authors.initials: JS
authors.lastname: Rufián
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterranea "La Mayora", Universidad de Malaga-Consejo Superior de Investigaciones Cientificas (IHSM-UMA-CSIC), Departamento Biologia Celular, Genetica y Fisiologia, Campus de Teatinos, Malaga E-29071, Spain.
authors.forename: Alberto P
authors.initials: AP
authors.lastname: Macho
authors.affiliation: Centre for Research in Bioscience, Faculty of Health and Applied Sciences, University of the West of England, Frenchay Campus, Bristol, BS16 1QY, UK.
authors.forename: David S
authors.initials: DS
authors.lastname: Corry
authors.affiliation: Faculty of Natural Sciences, Imperial College London, London, SW7 2AZ, UK.
authors.forename: John W
authors.initials: JW
authors.lastname: Mansfield
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterranea "La Mayora", Universidad de Malaga-Consejo Superior de Investigaciones Cientificas (IHSM-UMA-CSIC), Departamento Biologia Celular, Genetica y Fisiologia, Campus de Teatinos, Malaga E-29071, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Ruiz-Albert
authors.affiliation: Centre for Research in Bioscience, Faculty of Health and Applied Sciences, University of the West of England, Frenchay Campus, Bristol, BS16 1QY, UK.
authors.forename: Dawn L
authors.initials: DL
authors.lastname: Arnold
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterranea "La Mayora", Universidad de Malaga-Consejo Superior de Investigaciones Cientificas (IHSM-UMA-CSIC), Departamento Biologia Celular, Genetica y Fisiologia, Campus de Teatinos, Malaga E-29071, Spain.
authors.forename: Carmen R
authors.initials: CR
authors.lastname: Beuzón
mesh_terms: D018613:Microscopy, Confocal / Q000379:methods*; D010935:Plant Diseases / Q000382:microbiology*; D010944:Plants / Q000382:microbiology*; D044224:Pseudomonas syringae / Q000472:pathogenicity*; D000069296:Type III Secretion Systems / Q000378:metabolism; D014774:Virulence
chemical_list: D000069296:Type III Secretion Systems
keywords: avirulence; bacterial pathogen; colonization; defence suppression; effectors; type III secretion system; virulence