dam- e. coli

[Erik Boye]

Re: problems in transforming dam- strains of e. coli. A methylated plasmid will 
    after one round of replication become hemimethylated in a dam- host.
    Several origins of replication (chromosomal and plasmid) are poorly 
    initiated when hemimethylated. Tranformation efficiency is both strain and
    vector (origin) dependent. Unmethylated plasmids usually transform
    dam- hosts with high efficiency. So, when in trouble, switch host cell or
    switch to another cloning vector (preferably high copy number).
From: eboye at radium.uio.no