In article <malexeyev-2111952010510001 at 188.8.131.52>,
malexeyev at biost1.thi.tmc.edu says...
>Dna-gyrase is required for DNA replication, so all common laboratory
>E.coli strains should have it. gyrA96 mutation, if I am not mistaken, does
>not eliminate gyrase protein, but makes it relatively insensitive to
>inhibition by nalidixic acid...
Ahem! I *didn't* say that strains were gyr- for that very reason. I
simply said that they didn't have the appropriate gyr phenotype.
>Regarding previous discussion that I missed: is that true tha gyrA96
>mutation makes DNA gyrase less succeptible to inhibition by ccd?
This is what I have been led to believe. However, I have no personal
experience and am ready to be corrected on this point. Also, just to
confirm, Invitrogen appears to supply TOP10F' with pZerO-1 and this
strain does not have a gyrase mutation listed.
There are interesting implications for confirming/denying
the susceptibility of gyrA96 strains as Invitrogen say that it is
very difficult to grow the plasmid without an insert (especially in
strains without LacIq). If JM109/XL-1 Blue etc. are less sensitive
they would make good hosts for propagation of pZerO-1, if not for
the positive selection.
Disclaimer: I may not know what I am talking about. I am an occasional
customer of Invitrogen, but that's all.
Bernard Murray, Ph.D.
bernard at elsie.nci.nih.gov (National Cancer Institute, NIH, Bethesda MD, USA)