Rev 08/24/2026
Synonyms:
Review general morphological characteristics of genus Steinernema
Steinernema innovationi (isolate SGI-60) from South Africa belongs to the Khoisanae-clade, referred to as the all-African clade, as all the members of the clade have been isolated from South Africa (Cimen et al., 2015; Puza et al., 2025)
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:
Described from South Africa.
The dauer stage infective juvenile invades invades the body of the host insect and resumes development it releases releasing endosymbiotic pathogenic bacteria (Xanorhabdus sp in this case) from its intestine into the host. The nematode and bacterial symbiont kill the insect and convert the carcass into an incubator for the nematode-bacterial pair. When the carcass is exhausted of nutrients, a subsequent generation of IJs, each carrying pathogenic bacteria, disperse into the soil. (Dziedziech et al. 2020).
A new symbiotic bacterium species, Xenorhabdus innovationi, was isolated by Ritter et al (2026) from Steinernema innovationi in soil samples from a field in Bethlehem, South Africa. Strain SGI60 of the bacterium is gram-negative, rod-shaped, produces lecithinase and lipase, and lacks catalase and oxidase activity.
Juveniles of Steinernema innovationi cultured in vitro with strain SGI-60, and used to infect last-instar false codling moth larvae (Thaumatotibia leucotreta), killed 64% of the larvae within 48 h. The S. innovationi- X. innovationi associatoion is considered potentially useful for biological control agent for insect pests of crops (Ritter et al., 2026).
The following criteria characterize the general biology of entomopathogenic nematodes (a modification of Koch's postulates):
Ref: Dillman, et al., 2012; Ye et al., 2018).
Xenorhabdus is a genus of motile, gram-negative proteobacteria from the family of the Morganellaceae. Species of the genus are only known to live in symbiosis with Steinernema spp.
The nematode cannot establish within the insect host without the bacteria.
Some species of Xenorhabdus are virulent when injected directly into the insect host while other species appear to need phoresy with the nematode into the insect (Gaudriault et al, 2014).
Species of the genus Xenorhabdus (family Morganellaceae, order Enterobacterales) participate in a facultative to obligate symbiotic association with entomopathogenic nematodes (EPNs) of the Steinernema genus. The relationship with Xenorhabdus is essential to the fitness of the nematode as the bacterial symbiont help to kill and pre-digest arthropod prey (San-Blas et al., 2024). Cells of Xenorhabdus are contained in a specialized intracellular bacterial receptacle locatede just posterior to the esophago-intestinal junction in the nematode.
The bacteria are released into the hemocoel of the insect upon infection. Following release, both the nematode and its bacterial symbiont produce a diverse array of secondary metabolites with antimicrobial and insecticidal properties; the metabolites causehost mortality through septicaemia (Dreyer et al., 2018; Lu et al., 2017).
Ecophysiological Parameters:
Entomopathogenic nematodes.
Cimen, H., Lee, M.M., Hatting, J., Hazir, S. and Stock, S.P. 2015. Steinernema innovationi n. sp. (Panagrolaimomorpha: Steinernematidae), a new entomopathogenic nematode species from South Africa. Journal of Helminthology 89: 415- 427. DOI: 10.1017/S0022149X14000182
Dreyer, J., Malan, A.P. and Dicks, L.M.T. 2018. Bacteria of the genus Xenorhabdus, a novel source of bioactive compounds. Frontiers in Microbiology 9, 3177. DOI: 10.3389/FMICB. 2018.03177
Lu, D., Macchietto, M., Chang, D., Barros, M.M., Baldwin, J., Mortazavi, A. & Dillman, A.R. (2017). Activated entomopathogenic nematode infective juveniles release lethal venom proteins. PLoS Pathogens 13, e1006302. DOI: 10. 1371/JOURNAL.PPAT.1006302
Puza, V., Machado, R.A.R. and Malan, A.P. 2025. Biogeography, systematics, diversity and biogeography of entomopathogenic nematodes and their bacterial symbionts. Journal of Invertebrate Pathology 211: 108362. DOI: 10.1016/j. jip.2025.108362
Ritter, C.L., Wessels, H.L., Ramakuwela, T., Hatting, J., Malan, A.P., Dicks, L.M.T. 2026. Xenorhabdus innovationi sp. nov., associated with the entomopathogenic nematode Steinernema innovationi from South Africa. Nemastology 28: 195-208.
San-Blas, E., Sulbaran, Y. and Lankin, G. 2024. The biology of entomopathogenic nematodes as biological control agents. In: Shapiro-Ilan, D.I. & Lewis, E.E. (Eds). Entomopathogenic nematodes as biological control agents. Wallingford, UK, CAB International, pp. 40-58. DOI: 10. 1079/9781800620322.0002
Shapiro-Ilan, D. I., Gouge, D. H. and Koppenhofer, A. M. 2002. Factors affecting commercial success: case studies in cotton, turf and citrus, In Gaugler, R. (Ed.), Entomopathogenic Nematology CABI Publishing, Wallingford, pp. 333-356.
Spiridonov, S. E. and Subbotin, S. A. 2016. Phylogeny and phylogeography of Heterorhabditis and Steinernema. In: Hunt, D.J. & Nguyen, K.B. (Eds). Advances in entomopathogenic nematode taxonomy and phylogeny. Nematology Monographs and Perspectives 12 (Series Editors: Hunt, D.J. & Perry, R.N.). Leiden, The Netherlands, Brill, pp. 413-427. DOI: 10.1163/9789004285347_007
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