Seeding Problems

I work in a C. elegans lab at the University of Michigan and another undergrad and myself are struggling with seeding c. elegans plates with OP50

For the past year we haven’t had any problems with pouring and seeding worm plates using OP50 but recently we’ve run into several

First after pouring and allowing to dry, upon seeding the plates with between 100-300ul’s of OP50, the spots take and unusually long time to dry. Usually they dry overnight but we are finding they still are not dry after 2 days.

Also, when they eventually dry we’re noticing that the food is unusually moist making it extremely difficult to pick worms. Their usual paths, which were noticeable in the past, are no longer visible and the food is a brownish color.

We have tried several different cultures of OP50 from several labs to correct the problem but are still having trouble obtaining seeds like we have earlier this year.

We considered the change in humidity in the summer, we attempted to combat this problem by allowing the plates dry longer before and after seeding but still have had unfavorable results.

If there is any advice that anyone can offer it will be greatly appreciated, we would like to continue our projects but need some advice

If your lab is really humid, your plates will never dry out even if you leave them on a bench for days. In my case, a day or two after pouring and another day or two after seeding produces sufficiently dry plates, but if I need to pour and seed plates in a hurry I dry them out in a basic laminar flow hood. A chemical fume hood probably won’t work as well (and they’re usually very dirty…). You could also use a spare tissue culture hood, though you should negotiate that with tissue culture people who are understandably afraid of contamination.

Hi there.

Usually my colleagues and me would lit on Bunser burner in the laminar flow hood during the air-dry… we let it on for 20–30 mins, and it worked well all the time for us.


It is not surprising that it takes more than two days for a 300ul seeding to dry up on a freshly made, non-vented plate.
Humidity in summer contributes as well.
It seems there is sth. else involved in your problem. Is the bacterial lawn shiny and sticky? Have you changed any chemicals used in NGM or LB recently?

I am running a media kitchen in Ann Arbor. I supply worm plates to labs across the country. Give me a call at 734-761-8148. I will be happy to stop by and take a look of your plates If you are on U of Mich Ann Arbor campus . It is a pity if you have to call off the project because of the plate problem.

Sheila Wang
LabExpress----we make your research more efficient

Your problem is definitely plates that are still too wet. I typically leave our NGM plates out at room temperature for 3 days during the winter and sometimes longer during the summer. I also prefer plates that have sat around in the cold room for some time because they dry out even more. I have used plates that are 2-3 months old (not seeded yet) with no problems. Instead of squirting an aliquot and then spreading it to seed plates, I put 4 drops from a Pasteur pipet in a square shape on the plate and don’t spread them. When they dry, each makes a circle that is handy to view in the field of a dissecting scope. That way, I don’t lose track of where I’m at on a plate. Just check the four circles and you’re done.