Improved bacterial hosts for regulated expression of genes from λ, pL plasmid vectors

Abstract The construction and use of a set of Escherichia coli strains with defective λ prophages that facilitate expression of genes cloned in λ p L -plasmid vectors is described. These bacteria allow high and regulated expression of such genes, whereas a kanamycin-resistance marker (Km R ) on the prophage allows easy identification and genetic transfer from strain to strain. Optimal conditions for examining gene expression with the p L -vector systems using these strains are discussed.