BL21 problem

[Philipp Wechner]

Hi!

I have a problem with my BL21 stocks.

After electroporation i grow my BL21 on LB-agar containing the
antibiotic for selection of those cells which took up a plasmid.
the next day i always see some colnies that are much bigger than the
rest.

to see if this is a contamination in my stock i picked a single colony
and grew a new stock of it. same problem after this.
i do not have this problem with my DH5alpha, HMS174 and JM109.

The problem seems to be independent from the plasmid i am transforming.
What i also observed is that these colonies do not express my protein
correctly.

why do i only get these big colonies with BL21?

any ideas?


--
cu Philipp
(answers to the above email-adress are not read daily)