how to regain the desired strain from the contaminated E. coli stock?

Question

E.coli C600 thi-1 thr-1 leuB6 lacY1 recA1 supE44 mcrA

Answer 1

K.C.'s answer works if you have a selective media that will work. Also (or in addition to that) you may want to plate out colonies and then PCR out a unique sequence or two.

This wouldn't be definitive but if you design your primers right it may work, but also may be very time consuming.

Also you may want to try restriction digests to remap your gene. This would work well, if you have a good map.

Good luck, what a bummer

Answer 2

Probably the best way to do it would be to streak the culture out to isolate single colonies for testing. Given the presence of a few available mutations, you could then screen individual colonies by replica plating onto minimal media (such as M9) with or without the indicated nutrients such as leucine or threonine. If it grows as appropriate, dependent upon the added nutrient, you will have at least asserted the chance that it is the correct strain. If the contaminant is a much faster grower then you might have a difficult time. C600 actually has a few more auxotrophies that you can select for also.

Answer 3

My first thougt would be selective media, based on whatever your strain can metabolize.