Is it essential to add cholesterol to agar or liquid culture for C. elegans? In preparing agar plates with NGM, and also liquid cultures for growing c elegans, how essential is the addition of cholesterol and heavy metals? I have prepared both. I can't notice any obvious difference and I hate having to add all these supplements. I'm using yeast extract and peptone as the primary components of the base. Isn't this just supposed to be a moist semi-soft substrate for them to crawl around, their nutrients come from the bacteria they eat.

_C. elegans_ needs cholesterol, but can't make it. Since bacteria don't make cholesterol either, the food bacteria aren't a source. As explained in the linked paper, lack of cholesterol affects normal development.