Physical and Functional Characteristics of R-Factor Deoxyribonucleic Acid Segregated into Escherichia coli Minicells

Abstract

Both fi + and fi − type R factors function as intact replicative units when segregated into Escherichia coli minicells. Hybridization studies demonstrate that at least 95% of the deoxyribonucleic acid (DNA) in R + minicells is episomal in origin. About half of the DNA can be extracted in a closed circular form and about 75% of the DNA is membrane associated. DNA, ribonucleic acid, and protein synthesis proceeds in R + minicells in contrast to R − minicell controls. The system offers a unique opportunity to study a relatively small replicative unit in a native cell environment and a simple means of isolating large quantities of episomal DNA.