The insect pathogenic bacterium Xenorhabdus innexi has attenuated virulence in multiple insect model hosts yet encodes a potent mosquitocidal toxin

BMC Genomics

Research Article

Jean-Claude Ogier¹  Sophie Gaudriault¹  Michael P. Kozuch²  Ángel M. Casanova-Torres²  Dariush T. Aghai²  Jerald C. Ensign²  Kai Hillman²  Terra J. Mauer³  Erin J. Mans³  Heidi Goodrich-Blair³  Walter G. Goodman⁴  Il-Hwan Kim⁵  Adler R. Dillman⁶  Sudarshan K. Aryal⁶ 

[1] DGIMI, INRA, Université de Montpellier, 34095, Montpellier, France;Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA;Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA;Department of Microbiology, University of Tennessee-Knoxville, Knoxville, TN, USA;Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA;Department of Entomology, University of Wisconsin-Madison, Madison, WI, USA;Present address: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, Rockville, MD, USA;Department of Nematology, University of California, Riverside, CA, USA;

关键词: Virulence;    Toxin;    Symbiosis;    Insect;    Immunity;    NRPS/PKS;    Mosquito;    Lipopeptide;   

DOI  :  10.1186/s12864-017-4311-4

 received in 2017-06-07, accepted in 2017-11-16,  发布年份 2017

来源: Springer

【 摘 要 】

BackgroundXenorhabdus innexi is a bacterial symbiont of Steinernema scapterisci nematodes, which is a cricket-specialist parasite and together the nematode and bacteria infect and kill crickets. Curiously, X. innexi expresses a potent extracellular mosquitocidal toxin activity in culture supernatants. We sequenced a draft genome of X. innexi and compared it to the genomes of related pathogens to elucidate the nature of specialization.ResultsUsing green fluorescent protein-expressing X. innexi we confirm previous reports using culture-dependent techniques that X. innexi colonizes its nematode host at low levels (~3–8 cells per nematode), relative to other Xenorhabdus-Steinernema associations. We found that compared to the well-characterized entomopathogenic nematode symbiont X. nematophila, X. innexi fails to suppress the insect phenoloxidase immune pathway and is attenuated for virulence and reproduction in the Lepidoptera Galleria mellonella and Manduca sexta, as well as the dipteran Drosophila melanogaster. To assess if, compared to other Xenorhabdus spp., X. innexi has a reduced capacity to synthesize virulence determinants, we obtained and analyzed a draft genome sequence. We found no evidence for several hallmarks of Xenorhabdus spp. toxicity, including Tc and Mcf toxins. Similar to other Xenorhabdus genomes, we found numerous loci predicted to encode non-ribosomal peptide/polyketide synthetases. Anti-SMASH predictions of these loci revealed one, related to the fcl locus that encodes fabclavines and zmn locus that encodes zeamines, as a likely candidate to encode the X. innexi mosquitocidal toxin biosynthetic machinery, which we designated Xlt. In support of this hypothesis, two mutants each with an insertion in an Xlt biosynthesis gene cluster lacked the mosquitocidal compound based on HPLC/MS analysis and neither produced toxin to the levels of the wild type parent.ConclusionsThe X. innexi genome will be a valuable resource in identifying loci encoding new metabolites of interest, but also in future comparative studies of nematode-bacterial symbiosis and niche partitioning among bacterial pathogens.

【 授权许可】

CC BY   
© The Author(s). 2017