OP50 Problems

[Sam Smith]

We use OP50 and notice 2 problems. One, we get "dots" of abnormal
colonies within the main lawn. Two, every once in a while the OP50 is
a fast growing mass that has a thick crusty look to it rather than
being a loose colony. We've done everything we can think of to resolve
these problems, like constantly streaking new colonies for our LB,
making smaller portions of LB so the OP is not very old (2 months),
sterilizing any tools, and ordering new stock from the elegans
center.

Have others had this problem? Is this most likely a contamination
problem, or can the OP just be accumulating common mutations that
result in this phenotype?

The problem with this stuff is that with this crusty bacteria, it
pellets with the worms and can't be separated.

TIA

[Sam Smith]

I wanted to followup on the "crusty" bacteria situation. I received
quite a few helpful responses; thank you all. I think the most
plausible explanation is that there is too much Calcium in our plates
as our lab tech recently made - using the same OP50 stock - several
trays with this crusty stuff and 2 trays of perfect lawns.
Coincidentally, she also had to make new solutions of CaCl2 yesterday
because we were getting low. I'm thinking that she made the good agar
first as the CaCl2 was getting low, then mixed the contents (as
usually there is some precipitate at the bottom of old bottles), and
voila: bad plates! I'll need to watch this in the future to make
absolutely sure, but it really does seem to explain our problem. I
hope this is helpful to your labs!

As for the "dots", the jury is out. When I find out for sure, I'll
post.

[lijx...@gmail.com]

在 2010年12月2日星期四 UTC+8上午6:46:31，Sam Smith写道：

Hi Sam,
This is Sally, who also met the problem you encountered at that time.
I am writing to ask for your advise for getting rid of the "dots" and other contaminent. Hoping my enquiry is not disturbing.
Actually, I as well met some other kind of contamination. As I already changed the LB and picker, and still get the contamination. It really frustrating.
Have you already figure out what happend about to the OP50? Would you mind sharing your experience?
Thank you for your time and looking forward for your reply.
Sincerely yours,
Sally