Active resistance of entomophagous rhabditid Heterorhabditis bacteriophora to insect immunity.
A specific extracellular proteinase, degrading selectively the cecropin-based defence system of insects, is secreted into the larval body during parasitism of the greater wax moth by the Heterorhabditis bacteriophora/Photorhabdus luminescens complex and by phase 1 of P. luminescens. The proteolytic digestion of insect inducible cecropin-like immune molecules was demonstrated by the disappearance of the Galleria mellonella cecropins and purified Hyalophora cecropin B peptide PAGE bands upon exposure to infected extracts, and a similar abrogation of antibacterial activity using an agar diffusion assay. Proteolytic activity of infected extracts produced by nematode/bacterial complex and phase 1 variant of P. luminescens was shown to be correlated with cecropin-inhibitory activity, suggesting that this anti-cecropin agent may be responsible for the ability of bacteria to establish infection and the insecticidal nature of H. bacteriophora. Antibacterial activity of Galleria lysozyme and that of chicken egg-white lysozyme to which P. luminescens is insensitive, was unaffected by H. bacteriophora proteinase.
Department of Insect Pathology, Marie Curie-Skłodowska University, Lublin, Poland. jarosz@biotop.umcs.lublin.pl
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D000818:Animals; D015169:Colony Count, Microbial; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000276:immunology / Q000378:metabolism*; D004755:Enterobacteriaceae / Q000201:enzymology / Q000276:immunology; D004926:Escherichia coli / Q000276:immunology; D006790:Host-Parasite Interactions; D019476:Insect Proteins / Q000276:immunology* / Q000378:metabolism; D009036:Moths / Q000276:immunology / Q000469:parasitology*; D009113:Muramidase / Q000276:immunology / Q000378:metabolism; D017172:Rhabditoidea / Q000201:enzymology / Q000276:immunology*; D013559:Symbiosis / Q000502:physiology
D019476:Insect Proteins; C031162:cecropin B protein, Insecta; D009113:Muramidase; D010450:Endopeptidases