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Three Gram-stain-negative, rod-shaped, non-spore-forming bacteria, BA1 T , Q614 T and PB68.1 T , isolated from the digestive system of Heterorhabditis entomopathogenic nematodes, were biochemically and molecularly characterized to clarify their taxonomic affiliations. The 16S rRNA gene sequences of these strains suggest that they belong to the Gammaproteobacteria, to the family Morganellacea , and to the genus Photorhabdus . Deeper analyses using whole genome-based phylogenetic reconstructions suggest that BA1 T is closely related to Photorhabdus akhursti , that Q614 T is closely related to Photorhabdus heterorhabditis, and that PB68.1 T is closely related to Photorhabdus australis. In silico genomic comparisons confirm these observations: BA1 T and P. akhursti 15138 T share 68.8 % digital DNA-DNA hybridization (dDDH), Q614 T and P. heterorhabditis SF41 T share 75.4 % dDDH, and PB68.1 T and P. australis DSM 17609 T share 76.6  % dDDH. Physiological and biochemical characterizations reveal that these three strains also differ from all validly described Photorhabdus species and from their more closely related taxa, contrary to what was previously suggested. We therefore propose to classify BA1 T as a new species within the genus Photorhabdus , Q614 T as a new subspecies within P. heterorhabditis, and PB68.1 T as a new subspecies within P. australis . Hence, the following names are proposed for these strains: Photorhabdus aegyptia sp. nov. with the type strain BA1 T (=DSM 111180 T =CCOS 1943 T =LMG 31957 T ), Photorhabdus heterorhabditis subsp . aluminescens subsp. nov. with the type strain Q614 T (=DSM 111144 T =CCOS 1944 T =LMG 31959 T ) and Photorhabdus australis subsp . thailandensis subsp. nov. with the type strain PB68.1 T (=DSM 111145 T =CCOS 1942 T ). These propositions automatically create Photorhabdus heterorhabditis subsp . heterorhabditis subsp. nov. with SF41 T as the type strain (currently classified as P. heterorhabditis ) and Photorhabdus australis subsp. australis subsp. nov. with DSM17609 T as the type strain (currently classified as P. australis ).