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May 31, 2026INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY0 citations

Photorhabdus machadonis sp. nov. and Photorhabdus laumondii subsp. malanae subsp. nov., isolated from Heterorhabditis entomopathogenic nematodes

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ABAashaq Hussain BhatJKJavad KarimiSPSupawan Pansri

Key Points

  • This study aims to describe two novel bacterial taxa from Heterorhabditis nematodes and establish their phylogenetic relationships.
  • Isolation of strains from Heterorhabditis nematodes
  • Phylogenetic analysis using 16S rRNA and whole-genome sequences
  • Digital DNA–DNA hybridization for genetic comparison
  • P. machadonis sp. nov. is closely related to several Photorhabdus species with dDDH values of 48% to 54% and is proposed as a novel species.
  • P. laumondii subsp. malanae is established as a new subspecies with dDDH values of 73% and 79% to its closest relatives.
  • Biochemical characteristics of the novel taxa differ from those of closely related species, supporting their classification as new taxa.

Abstract

Two novel bacterial taxa, Photorhabdus machadonis sp. nov., represented by strain SF281 T , isolated from Heterorhabditis safricana SF281, and Photorhabdus laumondii subsp. malanae subsp. nov., represented by strain MH8.4 T , isolated from Heterorhabditis sp. eMH8.4TH, are described. Phylogenetic reconstruction using 16S rRNA shows that P. machadonis sp. nov. SF281 T is closely related to Photorhabdus cinerea DSM 19724 T , whereas P. laumondii subsp. malanae subsp. nov. MH8.4 T is closely related to P. laumondii subsp. laumondii TT01 T and P. laumondii subsp. clarkei BOJ-47 T . Phylogenetic reconstruction using whole-genome sequences shows that P. machadonis sp. nov. SF281 T is closely related to Photorhabdus tasmaniensis DSM 22387 T , Photorhabdus viridis Green T , Photorhabdus thracensis DSM 15199 T and Photorhabdus temperata DSM 14550 T , and P. laumondii subsp. malanae subsp. nov. MH8.4 T is closely related to P. laumondii subsp. laumondii TT01 T and P. laumondii subsp. clarkei BOJ-47 T . Digital DNA–DNA hybridization (dDDH) values between P. machadonis sp. nov. SF281 T and its four closest relative species P. tasmaniensis DSM 22387 T , P. viridis Green T , P. thracensis DSM 15199 T and P. temperata DSM 14550 T are 48%, 54%, 52% and 51%, respectively. dDDH values between P. laumondii subsp. malanae subsp. nov. MH8.4 T and its two closest sister species P. laumondii subsp. laumondii TT01 T and P. laumondii subsp. clarkei BOJ-47 T are 73% and 79%, respectively. The biochemical capacities of the novel taxa also differ from those of their more closely related taxa. Given the clear phylogenetic separation, the sequence divergence values and the phenotypic differences, we conclude that (i) strain SF281 T represents a novel bacterial species, for which we propose the name P. machadonis sp. nov. with SF281 T (=CCM 9463 T =CCOS 2127 T ) as the type strain, and (ii) strain MH8.4 T represents a novel bacterial subspecies, for which we propose the name P. laumondii subsp. malanae subsp. nov. with MH8.4 T (=CCM 9440 T =CCOS 2126 T ) as the type strain.

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Cite This Study

Bhat et al. (2026) studied this question.

synapsesocial.com/papers/6a1bd12d5783ba022b6fcc5ahttps://doi.org/10.1099/ijsem.0.007161
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