FIG. 1.

Schematic presentation of vector integration and inactivation of the genes ccpA, hprK, and ptsH. A fragment of L. monocytogenes EGD-e chromosomal DNA was cloned into the multiple cloning site of pLSV101 resulting in the plasmids pSM1 (ccpA), pSM2 (hprK), and pSM3 (ptsH). Replication of pSM1-3 in Listeria is stopped by increasing the temperature to 42°C. This selects for events in which pSM1-3 has integrated into the host chromosome by homologous recombination at the point of homology provided by the cloned DNA.