The construction of Streptomyces cyaneus genomic libraries in Escherichia coli is dependent upon the use of Mcr-deficient strains

Streptomyces cyaneus genomic DNA ligated into either λ phage or plasmid vectors was very inefficiently cloned into standard Escherichia coli host strains. However, the same material could be efficiently cloned using Mcr-deficient E. coli strains. These results suggest that the S. cyaneus genome contains 5-methylcytosine residues, some of which occur within the recognition sequences of the E. coli Mcr restriction system.