Is there anything beyond the appearance? Role of Surface components of entomopathogen nematodes and their symbionts bacteria.

Entomopathogenic nematodes (EPN) are symbiotic complexes widely used as bio-insecticides to control insects pests. The successful of the EPN results mostly from the neutralization of the host immune response carried out by both the nematode itself and by its symbionts bacteria. The structure and functions of the molecular components of the surface of the nematodes and of its bacteria could play a key role in the early interaction with the hosts. In this study we investigated the effects induced by surface compounds from both Steinernema carpocapsae (Nematoda, Rhabditidae) and its symbionts Xenorhabdus nematophila (Enterobacteriaceae) on Galleria mellonella (Insecta, Lepidoptera) larvae. We isolated and analysed by SDS-PAGE, high salts-soluble protein fractions (SoP) from the epicuticle/cuticle of nematodes or from bacteria cell wall (XoP); then, we have examined their cytotoxic effects on host haemocytes and their interference with phagocytosis activity of immunocompetent cells, finally we have assessed the modulatory properties on the host proPO system. EPN surface compounds seem to be involved in immunoevasion/depression of insect hosts leading to a general physiological disorder of the insect target. The search for new natural insecticide compounds could improve the control of species potentially invasive for urban greenery and agriculture, or harmful for human and animal health