Figure 1.

Schematic of λ Red-promoted PCR-mediated recombination. PCR products, containing a drug marker flanked by 40–60 bp of target DNA, are generated by primers designated 5KO and 3KO (see Table 6 in 2) and electroporated into EHEC containing pKM201 or pKM208 (or EPEC containing pTP223). Chromosomal replacements were verified by PCR using primers upstream (U), downstream (D) and within the drug marker (M) (data not shown).