P90: Induction of metabolite production by in vivo growth of Xenorhabdus and Photorhabdus spp

A number of bioactive metabolites have been isolated from the entomopathogenic (insect pathogenic) bacterial genera Xenorhabdus and Photorhabdus.  These bacteria live symbiotically  in the upper gut of soil nematodes that prey on soil living insect larvae.  When the nematodes invade an insect, they regurgitate their bacterial symbiont which begins to replicate.  Insecticidal toxins produced by the Xenorhabdus or Photorhabdus symbiont kill the insect and antifungal and antibacterial metabolites produced by the symbionts help preserve the insect carcass as a food source for both the bacteria and the nematode.  Since these bioactive metabolites play such a vital role in the life cycle of these organisms we investigated in vivo growth (in insects) as a method to induce production of bioactive metabolites by the symbionts.  Xenorhabdus and Photorhabdus isolates were injected into larvae of Spodopetera exigua (beet armyworm), after 2-3 days the insect carcasses were extracted and screened for bioactivity.  Growth in vivo was more effective in eliciting metabolite production than growth in vitro (TSB shake flask).  The metabolites and their bioactivities will be discussed.