Xenorhabdus aichiensis sp. nov., Xenorhabdus anantnagensis sp. nov., and Xenorhabdus yunnanensis sp. nov., Isolated from Steinernema Entomopathogenic Nematodes

Abstract

AbstractThree bacterial strains, XENO-2T, XENO-7T, and XENO-10T, isolated fromSteinernemaentomopathogenic nematodes, were found to represent novelXenorhabdusspecies. In this study, we describe these new species by whole-genome and whole-proteome phylogenomic reconstructions, by calculating sequence identity scores using core genome sequences, and by phenotypic characterization. Phylogenomic reconstructions using ribosomal and house-keeping genes, and whole-genome and whole-proteome sequences show that XENO-2Tand XENO-10Tare closely related toXenorhabdus japonicaDSM 16522Tand that XENO-7Tis closely related toXenorhabdus bovieniisubsp.africanaXENO-1Tand toX. bovieniisubsp.bovieniiT228T. The dDDH values between XENO-2Tand XENO-10Tand between XENO-2TandX. japonicaDSM 16522Tare 56.4 and 51.8%, respectively. The dDDH value between XENO-10TandX. japonicaDSM 16522Tis 53.4%. The dDDH values between XENO-7TandX. bovieniisubsp.africanaXENO-1Tand between XENO-7TandX. bovieniisubsp.bovieniiT228Tare 63.6 and 69.4%, respectively. These dDDH values are below the 70% divergence threshold for prokaryotic species delineation. The newly described species are highly pathogenic toG. mellonellalarvae, grow at pH between 5 and 9 (optimum 5–7), at salt concentrations of 1–3% (optimum 1–2%), and temperatures between 20 and 37 °C (optimum 28–30 °C). Biochemical tests such as lysine decarboxylase, ornithine decarboxylase, urease, gelatinase, citrate utilization, indole and acetoin production, and cytochrome oxidase tests allow to differentiate the novel species from their more closely related species. Considering these genetic and phenotypic divergencies, we propose the following new species:Xenorhabdus aichiensissp. nov. with XENO-7T(= CCM 9233T = CCOS 2024T) as the type strain,Xenorhabdus anantnagensissp. nov., with XENO-2T(= CCM 9237T = CCOS 2023T) as the type strain, andXenorhabdus yunnanensissp. nov., with XENO-10T(= CCM 9322T = CCOS 2071T) as the type strain. Our study contributes to a better understanding of the biodiversity and phylogenetic relationships of entomopathogenic bacteria associated with insect parasitic nematodes.