Photorhabdus khanii subsp. guanajuatensis subsp. nov., isolated from Heterorhabditis atacamensis, and Photorhabdus luminescens subsp. mexicana subsp. nov., isolated from Heterorhabditis mexicana entomopathogenic nematodes
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Two Gram-negative, rod-shaped, non-spore-forming bacteria, MEX20-17T and MEX47-22T, were isolated from the digestive system of Heterorhabditis atacamensis and Heterorhabditis mexicana entomopathogenic nematodes, respectively. Their 16S rRNA gene sequences suggest that strains MEX20-17T and MEX47-22T belong to the γ-Proteobacteria and to the genus Photorhabdus. Deeper analyses using housekeeping-gene-based and whole-genome-based phylogenetic reconstruction suggest that MEX20-17T is closely related to Photorhabdus khanii and that MEX47-22T is closely related to Photorhabdus luminescens. Sequence similarity scores confirm these observations: MEX20-17T and P. khanii DSM 3369T share 98.9 % nucleotide sequence identity (NSI) of concatenated housekeeping genes, 70.4 % in silico DNA-DNA hybridization (isDDH) and 97 % orthologous average nucleotide identity (orthoANI); and MEX47-22T and P. luminescens ATCC 29999T share 98.9 % NSI, 70.6 % isDDH and 97 % orthoANI. Physiological characterization indicates that both strains differ from all validly described Photorhabdus species and from their more closely related taxa. We therefore propose to classify MEX20-17T and MEXT47-22T as new subspecies within P. khanii and P. luminescens, respectively. Hence, the following names are proposed for these strains: Photorhabdus khanii subsp. guanajuatensis subsp. nov. with the type strain MEX20-17T (=LMG 30372T=CCOS 1191T) and Photorhabdus luminescenssubsp. mexicana subsp. nov. with the type strain MEX47-22T (=LMG 30528T=CCOS 1199T). These propositions automatically create Photorhabdus khanii subsp. khanii subsp. nov. with DSM 3369T as the type strain (currently classified as P. khanii), and Photorhabdus luminescenssubsp. luminescenssubsp. nov. with ATCC 29999T as the type strain (currently classified as P. luminescens).
author list (cited authors)
Machado, R., Bruno, P., Arce, C., Liechti, N., Köhler, A., Bernal, J., Bruggmann, R., & Turlings, T.