Antibiotic Activity of Xenorhabdus spp., Bacteria Symbiotically Associated with Insect Pathogenic Nematodes of the Families Heterorhabditidae and Steinernematidae
A wide range of microorganisms, including yeasts, was inhibited by the primary form of Xenorhabdus spp., but not by the secondary form. Only 1 Xenorhabdus strain, the symbiont of Neoaplectana glaseri, did not inhibit any of the microorganisms tested; this strain may not have been isolated in the primary form. Gram-positive bacteria were sensitive to all active isolates of Xenorhabdus; each of the yeasts and almost all of the gram-negative bacteria were sensitive to some but not all Xenorhabdus isolates. Each Xenorhabdus isolate was sensitive to some other Xenorhabdus isolates. The antibiotic activity of X. nematophilus was unaffected by autoclaving but was lost after dialysis. Anaerobically incubated Xenorhabdus spp. did not exhibit antibiotic activity.