Pathogenicity of bacterium, Xenorhabdus nematophila isolated from entomopathogenic nematode (Steinernema carpocapsae) and its secretion against Gaffer/a mellonella larvae

摘要

The entomopathogenic bacterium. Xenorhabdus nematophila was isolated from the hemolymph of Galleria mellonella infected with Steinernema carpocapsae. The bacterial cells and its metabolic secretions have been found lethal to the Galleria larvae. Toxic secretion in broth caused 95 percent mortality within 4 d of application whereas the bacterial cells caused 93 percent mortality after 6 d. When filter and sand substrates were compared, the later one was observed as appropriate. Similarly, bacterial cells and secretion in broth were more effective at 14 percent moisture and 25 deg C temperature treatments. Maximum insect mortality (100 percent) was observed when bacterial concentration of 4 X 10~6 cells/ml was used. Similarly, maximum bacterial cells in broth (95 percent) were penetrated into the insect body within 2 h of their application. However, when stored bacterial toxic secretion was applied to the insects its efficacy declined. On the other hand, when the same toxic secretion was dried and then dissolved either in broth or water was proved to be effective. The present study showed that the bacterium, X. nematophila or its toxic secretion can be used as an important component of integrated pest management against Galleria.