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

• DOI: 10.1186/s12864-017-4311-4
• Publication Date: 2017-12-01T02:50:45Z
• Authors: Il-Hwan Kim; Sudarshan K. Aryal; Dariush T. Aghai; Ángel M. Casanova...; Kai Hillman; Michael P. Kozuch; Erin J. Mans; Terra J. Mauer; Jean-Claude Ogier; Jerald C. Ensign; Sophie Gaudriault; Walter G. Goodman; Heidi Goodrich-Blair; Adler R. Dillman
• Keywords: Xenorhabdus; Entomopathogenic nematode; Galleria mellonella

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