In article <1995Nov3.155922.9875 at alw.nih.gov>, <ku at helix.nih.gov> wrote:
> There was a vector constructed some years ago that had the EcoRI
> endonuclease gene under tight temperature control. It worked very well
> if I remember correctly. I think it was called pEcoR251 and I can get
> more details if you need them.
I may add that one of these vectors (with EcoRI) endonuclease gene is
supposedly available from ATCC (check out their catalog). However, it took
me about 3 month of calling there to finally give up. The item was "out of
stock". Try them, may be they've managed to restock it. The EcoRV
restriction endonuclease gene produced up to 98-99% inserts in my hands,
strain- and site-dependent.
There are some other options, however. sacB gene of Bacillus subtilis is
lethal in the presence of sucrose (the gene is almost 2 kb long and often
does not rarely work up to published claims-- selection is not quite
straightforward, strain-to strain variation).
In general, bugs do not like to be pushed too hard and do find their way
around virtually any "killer". Therefore, efficiency of killing will
depend on genetic background of the strain.