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Ultracompetent E.coli cells!?! - Summary

Shin Enomoto shin at biosci.cbs.umn.edu
Sat Dec 16 08:36:42 EST 1995

Paul N Hengen (pnh at kaylor.ncifcrf.gov) wrote:
: Shin Enomoto (shin at biosci.cbs.umn.edu) wrote:

: | Can you explain further what cs means?

: : I meant cold-sensitive by cs.  I have not caculated how many divisions 
: : XL1-blue and DH5alpha are going through, but I am pretty sure they are 
: : not dividing efficiently.  Every other strain that I have tried to grow 
: : at 18C (SURE, MC1066, C600) I need to do at least 1/20000 dilution at 5pm 
: : to be harvesting at similar density as XL1-blue and DH5alpha.  I 
: : got 10^8 for MC1066 and C600 and 10^7 for SURE, but not 10^9.  I was 
: : wondering if high effeciency that I get sometimes with XL1-blue and 
: : DH5alpha had anyting to do with inability of these two strains to grow at 
: : low temperature.

: I don't think this is so. I know C600 has a shorter doubling time at 37C,
: somewhere around 12-15 min. as compared to 20-25 min. for HB101 and DH5a.
: A much longer time span at 18C is therefore expected for these strains.

Thanks for pointing that out.  I have done a crude caculation for the 
doubling time at 18C.  XL1-blue and DH5alpha are taking 3~4hrs to double 
and C600 is taking ~1hr to double.

I hope these numbers help for estimating how long to wait for you 
cultures to be ready.


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