title: Xenorhabdus bovienii CS03, the bacterial symbiont of the entomopathogenic nematode Steinernema weiseri, is a non-virulent strain against lepidopteran insects.
abstract: Xenorhabdus bacteria (γ-proteobacteria: Enterobacteriaceae) have dual lifestyles. They have a mutualistic relationship with Steinernema nematodes (Nematoda: Steinernematidae) and are pathogenic to a wide range of insects. Each Steinernema nematode associates with a specific Xenorhabdus species. However, a Xenorhabdus species can have multiple nematode hosts. For example, Xenorhabdus bovienii (Xb) colonizes at least nine Steinernema species from two different phylogenetic clades. The Steinernema-Xb partnership has been found in association with different insect hosts. Biological and molecular data on the Steinernema jollieti-Xb strain SS-2004 pair have recently been described. In particular, the Xb SS-2004 bacteria are virulent alone after direct injection into insect, making this strain a model for studying Xb virulence. In this study, we searched for Xb strains attenuated in virulence. For this purpose, we underwent infection assays with five Steinernema spp.-Xb pairs with two insects, Galleria mellonella (Lepidoptera: Pyralidae) and Spodoptera littoralis (Lepidoptera: Noctuidae). The S. weiseri-Xb CS03 pair showed attenuated virulence and lower fitness in S. littoralis in comparison to the other nematode-bacteria pairs. Furthermore, when injected alone into the hemolymph of G. mellonella or S. littoralis, the Xb CS03 bacterial strain was the only non-virulent strain. By comparison with the virulent Xb SS-2004 strain, Xb CS03 showed an increased sensitivity to the insect antimicrobial peptides, suggesting an attenuated response to the insect humoral immunity. To our current knowledge, Xb CS03 is the first non-virulent Xb strain identified. We propose this strain as a new model for studying the Xenorhabdus virulence.
authors.affiliation: Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Institut National de la Recherche Agronomique, 34095 Montpellier Cedex 05, France; Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Université Montpellier 2, 34095 Montpellier Cedex 05, 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, 34095 Montpellier Cedex 05, France; Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Université Montpellier 2, 34095 Montpellier Cedex 05, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Pagès
authors.affiliation: Department of Entomology, University of Arizona, 1140 E. South Campus Dr., Tucson, AZ 85721-0036, United States; School of Animal and Comparative Biomedical Sciences, University of Arizona, 1117 E. Lowell St., Tucson, AZ 85721, United States.
authors.forename: John G
authors.initials: JG
authors.lastname: McMullen
authors.affiliation: Department of Entomology, University of Arizona, 1140 E. South Campus Dr., Tucson, AZ 85721-0036, United States.
authors.forename: S Patricia
authors.initials: SP
authors.lastname: Stock
authors.affiliation: Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Institut National de la Recherche Agronomique, 34095 Montpellier Cedex 05, France; Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Université Montpellier 2, 34095 Montpellier Cedex 05, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Duvic
authors.affiliation: Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Institut National de la Recherche Agronomique, 34095 Montpellier Cedex 05, France; Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Université Montpellier 2, 34095 Montpellier Cedex 05, 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, 34095 Montpellier Cedex 05, France; Diversité, Génomes et Interactions Microorganismes-Insectes (DGIMI), Université Montpellier 2, 34095 Montpellier Cedex 05, France. Electronic address: sgaudriault@univ-montp2.fr.
authors.forename: Sophie
authors.initials: S
authors.lastname: Gaudriault
mesh_terms: D000818:Animals; D054884:Host-Pathogen Interactions; D056724:Immunity, Humoral; D007814:Larva / Q000276:immunology / Q000382:microbiology; D009036:Moths / Q000276:immunology / Q000382:microbiology*; D009348:Nematoda / Q000382:microbiology*; D013559:Symbiosis; D014774:Virulence; D020593:Xenorhabdus / Q000472:pathogenicity* / Q000502:physiology
keywords: Galleria mellonella; Spodoptera littoralis; Steinernema; Virulence; Xenorhabdus bovienii