Photorhabdus khanii subsp. guanajuatensis subsp. nov., isolated from Heterorhabditis atacamensis, and Photorhabdus luminescens subsp. mexicana subsp. nov., isolated from Heterorhabditis mexicana entomopathogenic nematodes.

Two Gram-negative, rod-shaped, non-spore-forming bacteria, MEX20-17 and MEX47-22, were isolated from the digestive system of Heterorhabditis atacamensis and Heterorhabditis mexicana entomopathogenic nematodes, respectively. Their 16S rRNA gene sequences suggest that strains MEX20-17 and MEX47-22 belong to the γ-Proteobacteria and to the genus Photorhabdus. Deeper analyses using housekeeping-gene-based and whole-genome-based phylogenetic reconstruction suggest that MEX20-17 is closely related to Photorhabdus khanii and that MEX47-22 is closely related to Photorhabdus luminescens. Sequence similarity scores confirm these observations: MEX20-17 and P. khanii DSM 3369 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 MEX47-22 and P. luminescens ATCC 29999 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 MEX20-17 and MEXT47-22 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 MEX20-17 (=LMG 30372=CCOS 1191) and Photorhabdus luminescenssubsp. mexicana subsp. nov. with the type strain MEX47-22 (=LMG 30528=CCOS 1199). These propositions automatically create Photorhabdus khanii subsp. khanii subsp. nov. with DSM 3369 as the type strain (currently classified as P. khanii), and Photorhabdus luminescenssubsp. luminescenssubsp. nov. with ATCC 29999 as the type strain (currently classified as P. luminescens).