Photorhabdus

**Definition:** A genus of gram-negative bacteria existing symbiotically with nematodes of the family Heterorhabditidae (see RHABDITOIDEA). These nematodes infect a variety of soil-dwelling insects. Upon entering an insect host, the nematode releases Photorhabdus from its intestinal tract and the bacterium establishes a lethal septicemia in the insect.

**Tree numbers:** - B03.440.450.425.590 - B03.660.250.150.545