Xenorhabdus and Photorhabdus bacteria are symbionts of entomopathogenic nematodes of the genera Steinernema and Heterorhabditis, respectively. To determine the nutrient potential of these bacteria for a free-living nematode, Panagrellus redivivus, a promising food source for first-feeding fish and crustacean, sterile first-stage juveniles (J1) of P. redivivus were fed on various isolates of Xenorhabdus and Photorhabdus bacteria in liquid cultures. Most of the tested bacterial isolates did not support the growth of P. redivivus. However, four of the Xenorhabdus isolates (X. nematophila All, X. bovienii T319, X. beddingii X-7 and X. poinarii KG) provided nutrients for the production of these nematodes in a liquid medium. Two Xenorhabdus isolates (X. beddingii X-7 and X. poinarii KG) even supported mass production of the nematode in a sponge medium, with yields comparable to those with yeast strains. This is the first report that Xenorhabdus bacteria can function as a nutrient source for mass production of nematodes other than their usual symbiotic partners.