title: Attenuated virulence and genomic reductive evolution in the entomopathogenic bacterial symbiont species, Xenorhabdus poinarii.
abstract: Bacteria of the genus Xenorhabdus are symbionts of soil entomopathogenic nematodes of the genus Steinernema. This symbiotic association constitutes an insecticidal complex active against a wide range of insect pests. Unlike other Xenorhabdus species, Xenorhabdus poinarii is avirulent when injected into insects in the absence of its nematode host. We sequenced the genome of the X. poinarii strain G6 and the closely related but virulent X. doucetiae strain FRM16. G6 had a smaller genome (500-700 kb smaller) than virulent Xenorhabdus strains and lacked genes encoding potential virulence factors (hemolysins, type 5 secretion systems, enzymes involved in the synthesis of secondary metabolites, and toxin-antitoxin systems). The genomes of all the X. poinarii strains analyzed here had a similar small size. We did not observe the accumulation of pseudogenes, insertion sequences or decrease in coding density usually seen as a sign of genomic erosion driven by genetic drift in host-adapted bacteria. Instead, genome reduction of X. poinarii seems to have been mediated by the excision of genomic blocks from the flexible genome, as reported for the genomes of attenuated free pathogenic bacteria and some facultative mutualistic bacteria growing exclusively within hosts. This evolutionary pathway probably reflects the adaptation of X. poinarii to specific host.
authors.affiliation: INRA, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Montpellier, FranceUniversité Montpellier 2, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Ogier
authors.affiliation: INRA, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Montpellier, FranceUniversité Montpellier 2, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Pagès
authors.affiliation: INRA, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Montpellier, FranceUniversité Montpellier 2, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), France.
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Bisch
authors.affiliation: INRA Toulouse Midi-Pyrénées, Unité MIA-T, Chemin de Borde Rouge, Castanet-Tolosan, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Chiapello
authors.affiliation: CEA, Genoscope & CNRS, UMR 8030, Laboratoire d'Analyse Bioinformatique en Génomique et Métabolisme, Evry, France.
authors.forename: Claudine
authors.initials: C
authors.lastname: Médigue
authors.affiliation: CEA, Genoscope & CNRS, UMR 8030, Laboratoire d'Analyse Bioinformatique en Génomique et Métabolisme, Evry, France.
authors.forename: Zoé
authors.initials: Z
authors.lastname: Rouy
authors.affiliation: Université Montpellier 1, UFR des Sciences Pharmaceutiques et Biologiques/UMR95 Qualisud, CIRAD-Persyst, France.
authors.forename: Corinne
authors.initials: C
authors.lastname: Teyssier
authors.affiliation: CEA, Genoscope & CNRS, UMR 8030, Laboratoire d'Analyse Bioinformatique en Génomique et Métabolisme, Evry, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Vincent
authors.affiliation: INRA, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Montpellier, FranceUniversité Montpellier 2, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Tailliez
authors.affiliation: INRA, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Montpellier, FranceUniversité Montpellier 2, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), France.
authors.forename: Alain
authors.initials: A
authors.lastname: Givaudan
authors.affiliation: INRA, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Montpellier, FranceUniversité Montpellier 2, UMR Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), France sgaudriault@univ-montp2.fr.
authors.forename: Sophie
authors.initials: S
authors.lastname: Gaudriault
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D017353:Gene Deletion; D016680:Genome, Bacterial; D023281:Genomics; D054884:Host-Pathogen Interactions; D007313:Insecta / Q000382:microbiology* / Q000502:physiology; D009348:Nematoda / Q000382:microbiology* / Q000469:parasitology* / Q000502:physiology; D010802:Phylogeny; D013559:Symbiosis; D037521:Virulence Factors / Q000235:genetics; D020593:Xenorhabdus / Q000235:genetics* / Q000472:pathogenicity* / Q000502:physiology
chemical_list: D037521:Virulence Factors
keywords: Lepidoptera; Steinernema; comparative genomics; entomopathogenic bacteria; genomic deletion; regions of genomic plasticity