Does anyone have experience with/information about long-term storage (as in 1-2 months+ then chunk and store again for 1-2 months+, then chunk again and repeat again, etc.) of plates with worms at 16C vs. 20C vs. 23-24C (RT)? The plates will obviously be starved after that long - is there any evidence that storing them at the 16C/20C (or lower?!) temperatures has any advantages over RT? I realize the best way is to freeze down for long term storage, but in the short term, I am helping to set up a lab where that is not possible. The strains would be N2 and some fluorescently labeled ones (not mutants). Thank you.
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I should say that for short term storage, I always put the plates into 16C. I am not sure about all the advantages but I realized that the if plates stay in 20C or more for 1 mouth, there will be full of fungi.
If your strains are sufficiently free of contamination, Parafilmed plates should be good for months. Lower temperatures (15C or 20C) seem to be better. There is some risk of a liquid seal forming between the plate and lid, which can asphyxiate the worms. This isn’t common but can happen, but can be prevented by cutting a notch out of the rim of the plate with a heated wire or spatula.
Maybe I’m just superstitious, but I don’t like to put fluorescent strains at 15C. We work mainly with fluorescent markers expressed in the germline and early embryo, and these seem to silence much more rapidly at 15 than at 20. I have recovered worms from 2-3 month old plates kept at 20C, as long as they don’t become badly contaminated. Parafilm will certainly help reduce the incidence of contamination.
“Maybe I’m just superstitious, but I don’t like to put fluorescent strains at 15C.”
It’s not necessarily superstitious at all. There is significant evidence that repetitive genomic sequences (including transgenes) in C. elegans will be more efficiently silenced at 15 deg. C. than at 20+ deg. C.
“Taken together, these results support the mechanistic model: At high temperature, SET-25 pathway activity is reduced, resulting in the derepression of many loci in the genome. After a return to low temperature, SET-25 activity is restored, but it takes multiple generations for repression to be completely reestablished. Expression from SET-25–repressed repeats therefore transmits information about a prior environmental exposure in this species.”
Reference: http://science.sciencemag.org/content/356/6335/320.full
Some of my labmates store their screening plates at 12C for a while and it works well, but your mileage may vary.