Liquid Culture of the Entomogenous Nematode Steinernema feltiae with Its Bacterial Symbiont

The insect-parasitic nematode, Steinernema feltiae Filipjev strain 42, was reared in liquid culture along with its bacterial symbiont, Xenorhabdus nematophilus Thomas &Poinar. First-stage juveniles developed into reproducing adults in a maintenance salts medium containing resuspended Xenorhabdus cells and the yeast Kluyveromyces marxianus (Hansen) van der Walt or cholesterol. Cultures with media depths greater than 4 mm required aeration. Nematode populations increased as bacterial density increased. An optimal culture system was obtained when the bacteria and nematodes developed in a semidefined medium containing tryptic soy, yeast extract, and cholesterol and were incubated on a rotary shaker at 25 +/- 1 C. Under these conditions, up to 86% of the final population were infective juveniles.