FIG 1 .

The mutualistic relationship between Xenorhabdus nematophila bacteria and Steinernema carpocapsae nematodes. (A) Cartoon depicting the tripartite life cycle of S. carpocapsae nematodes. Infective juveniles (IJs) infect an insect prey and release X. nematophila cells to evade the host immune system and kill the host. Both species use the cadaver’s nutrients for reproduction; upon nutrient depletion, the two organisms reassociate and enter the soil to begin the cycle again. (B to D) Confocal micrographs of the IJ stage of an S. carpocapsae nematode carrying GFP-expressing X. nematophila cells in the intestinal receptacle. The intravesicular structure (IVS) can be seen in panel D as the dark space below the white arrow and surrounded by bacterial cells.