Nomenclature relating to restriction of modified DNA in Escherichia coli

Abstract
At least three restriction systems that attack DNA containing naturally modified bases have been found in common Escherichia coli K-12 strains. These systems are McrA, McrBC, and Mrr. A brief summary of the genetic and phenotypic properties so far observed in laboratory strains is set forth, together with a proposed nomenclature for describing these properties.