FIG. 1.
Construction of E. coli strains in which TIRs originating from various genes are used to drive translation of the chromosomal lacZ gene. The DNA fragment carrying the TIR of interest (solid box) is first cloned in phase with the α-peptide gene (′lacZ′) of pEMBLΔ46, a pEMBL8+ derivative carrying a small deletion encompassing the lacZ RBS. The TIR is then transferred onto the chromosome of ENS0 by homologous recombination between lac sequences (lacI and lacZ) present on both the plasmid and chromosome. The chromosome of ENS0 (Lac−) carries a slightly larger lac deletion than the plasmid, encompassing the lac promoter (Plac) and operator (op).