FIG. 5.

Genetic organization at the chromosomal afsR locus of S. lividans strain NWR2. A previously described (24) gene replacement procedure was used to integrate the pIJ101 kilB gene at the S. lividans afsR locus. A 1.0-kb kilB-containing pIJ101 fragment was inserted into the afsR gene contained within the cloned S. lividans chromosomal afsR locus present on the thiostrepton-resistant, pUC19-based E. coli plasmid pBeBal2 (15, 23). Upon transformation of S. lividans strain TK23 with the resulting plasmid, pGSP295, integration of the plasmid at the chromosomal afsR locus by single reciprocal recombination between homologous sequences present on the plasmid and in the chromosome led to the genetic organization shown. The relative location of the afsR2 gene (23) within the afsR locus is also indicated. bla, beta-lactamase gene present within pUC19 sequences (unfilled box); tsr, thiostrepton resistance gene; afsR′ and ′afsR, interrupted portions of the afsR gene that resulted from insertion of the kilB-containing pIJ101 fragment.