Abstract:  Surface coat proteins (SCPs) of Steinernema glaseri were proved to play important roles in defeating the host immune system. SCPs suppress insect immune response and promote infection of entomopathogenic nematodes. In this study, influences of different culture media on SCPs were investigated, which may provide useful information for further studying the immunosuppressive mechanisms of SCPs and the relationship between entomopathogenic nematodes and their hosts. Infective juveniles of S. glaseri were reared on an artificial medium and the last (5th) instar larvae of Galleria mellonella, respectively, and the SCPs from these nematodes were extracted with ethanol. SDS-PAGE and native-PAGE analysis of SCPs indicated that SCPs from S. glaseri nematodes reared on G. mellonella displayed more protein bands than those from the nematodes reared on the artificial medium. SCPs from S. glaseri nematodes reared on G. mellonella larvae had intensive lytic activity against hemocytes of G. mellonella both in vitro and in vivo, while SCPs from the nematodes reared on the artificial medium showed weak lytic activity. Moreover, hemocyte lytic SCPs were found to be inducible proteins. Variation of components and activity of SCPs from nematodes reared on different culture media demonstrates that the production of SCPs mainly depends on culture environments.

Key words: Steinernema glaseri, surface coat proteins (SCPs), culture media, artificial medium, Galleria mellonella, hemocyte, lytic activity