What does 'just cleared of bacteria' mean?


I’ve been looking at the WormBook: WormMethods protocol for starting a liquid culture, and it mentions in the reagents section to use 4 large plates of C. elegans ‘just cleared of bacteria’.

Does this mean that you go through the full bleaching process as you would to clean a contaminated stock, and just use eggs to seed the culture? Or does it mean washing the worms in some way, or adding antibiotic to the plate?


“Just cleared” means the worms have recently finished eating the entire lawn of bacteria from the plate. It provides a large number of non-arrested (as opposed to dauer) worms to begin your liquid cultures.


Some protocols will also refer to a “wave” of animals, because as they start to finish eating the last of the bacteria the worms will move to the parts of the plate where the bacteria remain, and the resulting aggregation of worms will then move across the plate as they clear the remaining bacteria, like a noose tightening around the remaining lawn, very often with part of the “noose” forming a straight or nearly straight line moving across the plate (that “wave” I mentioned). If they have consumed all the bacteria, they will start to disperse; if they’re well dispersed, they may no longer be well fed.