Bacterial Chromosomes and PFGE

Mark Farinha mfarinha at
Fri Sep 2 10:16:19 EST 1994

In article <345o72$njr at>, lanoilb at (Brian_D Lanoil) says:
My problem: when I run E. coli on the gel as a control, I see multiple 
>bands.  Since E. coli has only one chromosome and this particular strain 
>has no plasmids, I am at a loss to explain what the extra bands are.  
>There is one band which runs at the correct size of ~4.5 Mb, but all of 
>the others are _larger_.

If the problem is one of incomplete replication forks so that you
are separating christmas tree structures, you can let your cultures
proceed into late log phase and/or add chloramphenicol which allows
rounds of replication to be completed but inhibits the initiation of
new rounds of replication.  This should give only the 4.5 MB chromosome.

good luck

Mark Farinha

University of Alberta      Biological Sciences

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