Pathogenicity of bacteria symbiotically associated with insect pathogenic nematodes against the greater wax moth, Galleria mellonella (L.)

摘要

The bacterial symbionts isolated from the entomopathogenic nematodes were compared for their pathogenicity to last instar larvae of G. mellonella at both Phases I and II. Most bacterial symbionts at Phase I caused 100% mortality within 2-3 days post-injection with 1 x 103 cells/larva. The pathogenicity of Phase I decreased in the following order: Xenorhabdus nematophilus, Flavimonas oryzihabitans, Photorhabdus luminescens and X. bovienii with LD50 values of 40, 55, 70 and 170 cells/larva, respectively. The injection of Phase II of the bacterial symbionts did not give 100% mortality even after 4 days post-injection. The time mortality response of G. mellonella larvae to both phases of the bacterial symbiont was significantly different usually at the two highest concentrations tested. Pathogenicity in Phase I was in the following order (from lowest to highest): F. oryzihabitans, X. nematophilus, P. luminescens and X. bovienii at 20.57, 23.96, 23.99 and 53.76 h, respectively. Also, F. oryzihabitansgave the lowest LT50 value (36.85 h) for its Phase II form, followed by X. bovienii (69.29 h), X. nematophilus (74.08 h) and P. luminescens (74.49 h). The results suggest that there is a direct correlation between toxin concentration and killing rate oflarvae. On the other hand, there is an inverse correlation between the LT50 values and the injected concentration.