pLysS freezer stock instability

Edward Beaty edbeaty at
Tue Mar 21 18:13:25 EST 1995

> In article <3k1qej$4ia at>, Frank van de Loo
<fvandelo at> writes:
> > Dear methodists,
> > I find that my BL21(DE3)pLysS competent cells, and pET-containing
> > strains derived from them, lose their chloramphenicol resistance
> > during storage at -80. 

Pardon me if this was in the original article, but I missed the first time
around.  Were you able to recover pLysS from the cells after regrowing
them?  I know that the lysozyme can cause strains with pLysS to lyse when
they get near freezing...maybe most of your plasmid-carrying cells are
lysing when you start to freeze them?  One time I was trying to prepare
electrocompetent BL21(DE3)pLysS I centrifuged my cells in a cold (4 C)
rotor...I ended up with a very gooey pellet.

Just a thought,
Edward Beaty
Department of Microbiology
University of Illinois-Urbana

Ed Beaty
Ed_Beaty at
"A mime is a wonderful thing to waste."

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