Worm Breeder's Gazette 8(2): 53
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
We have discovered a simple and convenient procedure for obtaining wild isolates of C. elegans. Many attempts to isolate wild-type strains by spreading soil samples on petri dishes were unsuccessful, but the following procedure yielded several isolates quickly. This procedure samples relatively large volumes of soil. It is essentially the same as the 'Baermann tray method' described in Methods for Evaluating Plant Fungicides, Nematicides and Bactericides, published by the American Phytopathological Society. The materials include 2 pie pans and a gauze milk filter (that's right -- a milk filter!). One pie pan is approximately 18 cm in diameter and 3.5 cm deep. The second is slightly smaller (approximately 17 cm diameter and 3 cm deep) and fits into the first; furthermore, it has a coarse wire mesh bottom (openings about 3.5 x 3.5 mm). The milk filter is approximately 19 cm in diameter and 2 mm thick. Cheesecloth might also work. Soil samples are sifted through the wire mesh pie pan and then through a 30-mesh wire sieve. This sifting removes debris and loosens the soil. The milk filter is placed over the mesh bottom of the smaller pie pan and covered with 2 facial tissues. A 50-100 ml sample of soil is spread evenly over the tissues and the smaller pan inserted into the larger one. The combination is filled with approximately 250 ml of water. This amount of liquid is sufficient to keep the soil saturated. The pan is covered with Saran Wrap and stored at room temperature for 3-7 days. Nematodes crawl through the filter and collect in the water. The nematodes can then be concentrated either by settling for several hours or by centrifugation. The worms are plated out on NGM agar and screened for those resembling C. elegans. ( Be prepared for a real zoo.) We collected soil from around the campus and isolated C. elegans from five different samples. Habitats ranged from a barnyard stock pen to a forest floor along the shores of Lake Mendoda. Southern blots show that four of these strains have a low copy number of Tc1 (similar to Bristol), while the fifth has a high copy number (similar to Bergerac).