competent bacteria

Anna Blom Anna.Blom at
Tue Feb 13 11:28:53 EST 1996


Does anyone has a good method of preparing competent bacteria that can be
My bacteria are OK as long as I do not freeze them (5x107cfu/ug). If I
freeze them they become almost useless - 105 cfu/ug. I use the standard
calcium method. I tried to add DMSO or glycerol while freezing bacteria
in liquid nitrogen, but it did not help. I also tried to grow bacteria in
low temperature (22°C) before treating them with calcium but... I have to
subclone quite large and difficult construct so I really need to have
highly competent bacteria. Of course I can buy some from some company but
they are terribly expensive.
Any good advises?

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