Additional Strains

Methylation-Free Plasmid Cloning in Clean Genome E. coli

DNA methyltransferases play an important role in restriction-modification systems in bacteria. DNA adenine methyltransferase (dam) has been shown to play a role in coordinating DNA replication initiation, DNA mismatch repair and the regulation of expression of some genes. DNA cytosine methyltransferase (dcm) appears to enhance viability during a prolonged stationary phase.

However, the activity of the DNA dcm and dam methyltransferase enzymes in bacteria harboring plasmids results in methylation at specific sites on the plasmid as it replicates. Although not generally a problem, plasmids generated in E. coli containing these genes cannot be transferred to methylation sensitive organisms. Plasmids propagated in these bacterial strains are also resistant to excision by restriction enzymes that overlap the sites targeted by dcm or dam (CCWGG or GATC, respectively).

Clean Genome strains are available that lack either the dcm gene or the dam gene or both. By using these modified strains, you can enjoy the benefits of Clean Genome competent cells while protecting your plasmid DNA from unwanted methylation. Use the form below to request access to dam-/dcm- Clean Genome E. coli strains.