Photorhabdus aballayi sp. nov. and Photorhabdus luminescens subsp. venezuelensis subsp. nov., isolated from Heterorhabditis amazonensis entomopathogenic nematodes

Abstract

Six Gram-negative, rod-shaped bacterial strains isolated fromHeterorhabditis amazonensisentomopathogenic nematodes were characterized to determine their taxonomic position. 16S rRNA andgyrBgene sequences indicate that they belong to the classGammaproteobacteria, familyMorganellaceaeand genusPhotorhabdus, and that some of them are conspecifics. Two of them, APURETand JART, were selected for further molecular characterization using whole genome- and whole-proteome-based phylogenetic reconstructions and sequence comparisons. Phylogenetic reconstructions using whole genome and whole proteome sequences show that strains APURETand JARTare closely related toPhotorhabdus luminescenssubsp.luminescensATCC 29999Tand toP. luminescenssubsp.mexicanaMEX47-22T. Moreover, digital DNA–DNA hybridization (dDDH) values between APURETandP. luminescenssubsp.luminescensATCC 29999T, APURETandP. luminescenssubsp.mexicanaMEX47-22T, and APURETand JARTare 61.6, 61.2 and 64.1 %, respectively. These values are below the 70 % divergence threshold that delimits prokaryotic species. dDDH scores between JARTandP. luminescenssubsp.luminescensATCC 29999Tand between JARTandP. luminescenssubsp.mexicanaMEX47-22Tare 71.9 and 74.8 %, respectively. These values are within the 70 and 79 % divergence thresholds that delimit prokaryotic subspecies. Based on these genomic divergence values, APURETand JARTrepresent two different taxa, for which we propose the names:Photorhabdus aballayisp. nov. with APURET(=CCM 9236T=CCOS 2019T) as type strain andPhotorhabdus luminescenssubsp.venezuelensissubsp. nov. with JART(=CCM 9235T=CCOS 2021T) as type strain. Our study contributes to a better understanding of the biodiversity of an important bacterial group with enormous biotechnological and agricultural potential.