title: Comparative Genomics between Two Xenorhabdus bovienii Strains Highlights Differential Evolutionary Scenarios within an Entomopathogenic Bacterial Species.
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. Within Xenorhabdus bovienii species, the X. bovienii CS03 strain (Xb CS03) is nonvirulent when directly injected into lepidopteran insects, and displays a low virulence when associated with its Steinernema symbiont. The genome of Xb CS03 was sequenced and compared with the genome of a virulent strain, X. bovienii SS-2004 (Xb SS-2004). The genome size and content widely differed between the two strains. Indeed, Xb CS03 had a large genome containing several specific loci involved in the inhibition of competitors, including a few NRPS-PKS loci (nonribosomal peptide synthetases and polyketide synthases) producing antimicrobial molecules. Consistently, Xb CS03 had a greater antimicrobial activity than Xb SS-2004. The Xb CS03 strain contained more pseudogenes than Xb SS-2004. Decay of genes involved in the host invasion and exploitation (toxins, invasins, or extracellular enzymes) was particularly important in Xb CS03. This may provide an explanation for the nonvirulence of the strain when injected into an insect host. We suggest that Xb CS03 and Xb SS-2004 followed divergent evolutionary scenarios to cope with their peculiar life cycle. The fitness strategy of Xb CS03 would involve competitor inhibition, whereas Xb SS-2004 would quickly and efficiently kill the insect host. Hence, Xenorhabdus strains would have widely divergent host exploitation strategies, which impact their genome structure.
authors.affiliation: Diversité, Génomes Et Interactions Microorganismes-Insectes (DGIMI), Institut National De La Recherche Agronomique, Montpellier Cedex, France Diversité, Génomes Et Interactions Microorganismes-Insectes (DGIMI), Université Montpellier, France.
authors.forename: Gaëlle
authors.initials: G
authors.lastname: Bisch
authors.affiliation: Diversité, Génomes Et Interactions Microorganismes-Insectes (DGIMI), Institut National De La Recherche Agronomique, Montpellier Cedex, France Diversité, Génomes Et Interactions Microorganismes-Insectes (DGIMI), Université Montpellier, France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Ogier
authors.affiliation: CEA, Genoscope & CNRS-UMR 8030, Laboratoire D'analyse Bioinformatique En Génomique Et Métabolisme, Evry Cedex, 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 Cedex, France.
authors.forename: Zoé
authors.initials: Z
authors.lastname: Rouy
authors.affiliation: CEA, Genoscope & CNRS-UMR 8030, Laboratoire D'analyse Bioinformatique En Génomique Et Métabolisme, Evry Cedex, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Vincent
authors.affiliation: Diversité, Génomes Et Interactions Microorganismes-Insectes (DGIMI), Institut National De La Recherche Agronomique, Montpellier Cedex, France Diversité, Génomes Et Interactions Microorganismes-Insectes (DGIMI), Université Montpellier, France.
authors.forename: Patrick
authors.initials: P
authors.lastname: Tailliez
authors.affiliation: Diversité, Génomes Et Interactions Microorganismes-Insectes (DGIMI), Institut National De La Recherche Agronomique, Montpellier Cedex, France Diversité, Génomes Et Interactions Microorganismes-Insectes (DGIMI), Université Montpellier, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Givaudan
authors.affiliation: Diversité, Génomes Et Interactions Microorganismes-Insectes (DGIMI), Institut National De La Recherche Agronomique, Montpellier Cedex, France Diversité, Génomes Et Interactions Microorganismes-Insectes (DGIMI), Université Montpellier, France sgaudriault@univ-montp2.fr.
authors.forename: Sophie
authors.initials: S
authors.lastname: Gaudriault
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D049810:Genetic Speciation; D016680:Genome, Bacterial; D009348:Nematoda / Q000382:microbiology; D011544:Pseudogenes; D014774:Virulence / Q000235:genetics; D020593:Xenorhabdus / Q000235:genetics* / Q000472:pathogenicity
keywords: competitor inhibition; entomopathogenic bacteria; insect; nematode; virulence