Regulation of replication of plasmid pBR322 in amino acid-starvedEscherichia colistrains

✍ Scribed by A. Herman; A. Węgrzyn; G. Węgrzyn

• Publisher: Springer
• Year: 1994
• Tongue: English
• Weight: 519 KB
• Volume: 243
• Category: Article
• ISSN: 1617-4615
• DOI: 10.1007/bf00280467

✦ Synopsis

The stringent response causes inhibition of replication of plasmid pBR322 in amino acid-starved Escherichia coli cells whereas in relaxed mutants the replication of this plasmid proceeds for several hours. On the basis of density shift experiments and pulse-labelling experiments we showed that most of the pBR322 molecules begin replication during the relaxed response and the rate of plasmid DNA synthesis in unstarved and isoleucine-starved relA- bacteria is similar. We found that the Rom function plays a key role in the stringent control of plasmid pBR322 replication, as insertional inactivation of the rom gene causes amplification of pBR322rom- in both relA- and relA+ strains during amino acid starvation. Moreover, pUC19, which is a pBR322-derived plasmid lacking the rom gene, behaves like pBR322rom-, whereas introduction of the rom gene into the pUC19 replicon drives it into the pBR322 mode of replication in amino acid-starved bacteria. A model for the regulation of pBR322 plasmid DNA replication by Rom protein in amino acid-starved Escherichia coli strains is proposed.