B Broth (for OP50 E. coli to feed to worms)
- 10 g bactotryptone
- 5 g NaCl
- 1 L dH2O
400 µL overnight culture to seed plates.
Store for months in refrigerator.
200 mL cells ON for 500 plates
(can save the extra ON culture in the refrigerator for 3 days.)
3.1. Preparation of bacterial food source
Although C. elegans can be maintained axenically (Avery, 1993), it is difficult, and the animals grow very slowly. C. elegans is usually grown monoxenically in the laboratory using E. coli strain OP50 as a food source (Brenner, 1974). E. coli OP50 is a uracil auxotroph whose growth is limited on NGM plates. A limited bacterial lawn is desirable because it allows for easier observation and better mating of the worms. A starter culture of E. coli OP50 can be obtained from the CGC or can be recovered from worm plates. Use the starter culture to isolate single colonies on a streak plate of a rich medium such as LB agar [10 g Bacto-tryptone, 5 g Bacto-yeast, 5 g NaCL, 15 g agar, H2 O to 1 litre, pH 7.5] (Byerly et al., 1976). Using a single colony from the streak plate, aseptically inoculate a rich broth, such as L Broth [10 g Bacto-tryptone, 5 g Bacto-yeast, 5 g NaCl, H2 O to 1 litre, pH to 7.0 using 1 M NaOH. Put 100 ml into 250 ml screw-cap bottles and autoclave. The bottles of media can be stored at room temperature for several months (Byerly et al., 1976)]. Allow inoculated cultures to grow overnight at 37°C. The E. coli OP50 solution is then ready for use in seeding NGM plates. The E. coli OP50 streak plate and liquid culture should be stored at 4°C and will remain usable for several months.