ABSTRACT
Entomopathogenic nematodes of the families Heterorhabditidae and Steinernematidae are lethal insect endoparasites characterized by their association with bacteria in the genera Photorhabdus and Xenorhabdus, respectively. This association is obligate mutualism in nature, with each partner requiring the other to complete its life cycle. Nematode growth and reproduction depend upon conditions established in the insect host by the bacterium. On the one hand, the bacteria contribute anti-immune proteins to assist the nematode in overcoming host defenses and antimicrobials that suppress competitors (Forst and Clarke, 2002). On the other, the bacteria lack invasive powers and are dependent upon the nematode to locate and penetrate suitable hosts. The nematode-bacterium complex is an important natural enemy of soil insects and plays a signi cant role in the regulation of soil food webs. Interest in their potential for use as biological insecticides has fueled decades of research.
