Fig. 1

Xenorhabdus bacteria and Steinernema nematode life cycle. In the soil, Steinernema infective juvenile (IJ) nematodes containing their Xenorhabdus symbionts seek out and invade insect hosts. Once in the insect blood cavity, the nematodes and bacteria produce virulence factors and kill the insect host. The nematodes and bacteria then grow and reproduce using insect cadaver biomass, a process facilitated by the bacterial symbiont. During reproduction, the growing nematodes and bacteria are vulnerable to insect predators and microbial competitors, and therefore, defensive compounds are produced during reproduction. Once all nutrients within the cadaver are consumed, the nematodes form the next generation of IJs (progeny) that then exit the insect cadaver to seek new insect hosts