Identification of a pWTY27 locus required for replication in Streptomyces lividans. (a). Identification of a replication locus. Plasmids were constructed in E. coli (see Methods and Table 1), and introduced by transformation into S. lividans ZX7. Positions of these cloned fragments on pWTY27 and transformation frequencies are shown. The ncs is indicated by striped boxes, relevant genes by open arrowheads and the two replication genes by filled arrowheads. (b). RT-PCR of a transcript overlapping the consecutive replication genes. RNA of strain Y27 was isolated and reverse-transcribed into cDNA. The cDNA, RNA and Y27 genomic DNA were used as templates for PCR amplification and their products were electrophoresed in 1.5% agarose gel at 20 V/cm for 1 h.