[
International C. elegans Meeting,
1991]
A microbial exometabolite (ME) has been isolated which inhibits egg- laying in Caenorhabditis elegans. Nematodes exposed to active concentrations of the factor, and maintained at 22C in axenic culture ( liver extract medium), mature and grow normally. Eggs are fertilized and larvae develop and move within eggs as in untreated nematodes. However, eggs are not laid, though occasionally hatch occurs within the gonad. In shake culture of the microbe, active yellow-pigmented ME appears at 3-4 days. A concentration of 8 parts ME: 1 part liver extract completely inhibits egg-laying. Concentrations of 4 ME: 1 liver extract and 2 ME: 1 liver extract, inhibit egg-laying about 50 and 25%, respectively. Sections from nematodes exposed to extracts of a microbe showing similar properties examined by transmission electron microscopy indicated that the constrictor and dilator muscles associated with vulval function in egg-laying appear normal. ME is thermostable (at 100C for 5 min.), and the active fraction does not pass through 6,000-8,000 MW dialysis tubing. About one-half of the activity is lost when ME is dialyzed through 12,000 14,000 MW membrane tubing, suggesting the presence of at least two active fractions. Trypsinization obliterated activity. Thus far, the double control experiment with trypsin inhibitor has not yielded definitive results. SDS gel electrophoresis of boiled ME, with molecules below 8,000 MW removed by dialysis, revealed several strong protein bands, one or more of which may be ME. ME purification and characterization studies continue.