%0 Journal Article %A Hadfield, Christopher %A Brammar, William J. %T A Genetic Analysis of Defective Plasmid Formation by N-deficient Phage λ Chromosomes %D 1984 %J Microbiology, %V 130 %N 10 %P 2501-2513 %@ 1465-2080 %R https://doi.org/10.1099/00221287-130-10-2501 %I Microbiology Society, %X Plasmid formation by N derivatives of lambdoid phages has been reinvestigated with transducing phages carrying the trp, lac and gal genes of Escherichia coli. Transduction by λN cI derivatives was inefficient and short-lived in each case, under both selective and nonselective conditions. Mutant operators were introduced to relieve possible auto-repression by the cro gene product. Such N-defective phage genomes were able to propagate continually as plasmids, although without selection they were gradually lost from the carrier cells. Plasmid formation remained inefficient, however. The entire chromosome of N phages can be expressed by transcription that leaks through the serially arranged Rho-dependent terminators. Some functions so expressed are deleterious to the plasmid state and cause the instability of λN plasmids. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-130-10-2501