Isolation of a Serratia marcescens mutant which is an efficient recipient for the E. coli episome

A Serratia marcescens mutant, which is an efficient recipient for the Escherichia coli episome (F' plasmid), was isolated after mutagenesis by N-methyl-N'-nitro-N-nitrosoguanidine (NTG). Episomes could be maintained in the mutant cell under conditions selective for a gene on the plasmid. This S. marcescens mutant could also be transformed with pBR 322 DNA at a frequency higher than that of the parental strain.