Strange goopy OP50

Hi All,

In our lab we are noticing some very strange OP50 growth on our NGM agar plates. We streak from a glycerol stock (original OP50 was ordered from CGC a few years ago) onto an LB agar plate and pick a single colony to inoculate a culture which we use to seed plates. All this is done with sterile technique (we have a sterile hood which we use). However, we have noticed that some of our plates (not all from the same batch) have pin prick colonies which are darker in colour and extremely goopy in texture. The worms seem to love the goop but we have noticed that eventually the goop spreads over the entire lawn of the plate and the worms seem to be getting a bit sick (definitely throws more sterile worms than usual). Our last batch of seeded plates didn’t have any pin prick colonies within the OP50 lawns but the entire lawns were of the goopy stuff.

The plates smell and the colour of the agar changes to a more orange colour than the greyish normal colour of NGM agar plates.

Has anyone else ever experienced anything like this or have any idea of what it could be?! Any comments on this topic would be most welcome - Thank you in advance.

It’s really hard to keep the cultures and plates 100% sterile, so we’ve definitely seen stuff like this before. They are really not usable, we just throw them out if we have bad bacteria like this and grow a new batch of OP50 from a fresh colony. I encourage my team to seed a couple test plates whenever they make a new batch of OP50 and let them sit for a couple of days before seeding a whole batch of plates with it. Also, we’re in very humid location and contamination is always worse during the summer. Hope the next batch is better!