Transcriptional and post-transcriptional control of RNA polymerase and ribosomal protein genes cloned on composite ColE1 plasmids in the bacterium Escherichia coli.

Unless otherwise specified, the bacterial strain employed was MV12, a thr, Zeu, thi, recA, trpE5 derivative of Escherichia coli C600.Isolation and characterization of the plasmids pJC701, 702, 703, and 720 has been described (Collins et al., 1976).Cultures were grown at 37°C in AB minimal medium supplemented with glucose (2 mg/ml), Thr (50 Pg/ml), Leu (50 pg/mI), Trp (50 ,ug/ml), and thiamin (0.5 mg/ ml) unless otherwise specified.