| Abstract: | The stability behaviour of the pBR322 plasmid derivative pBB210 with β-lactamase gene and human interferon-α1 gene in Escherichia coli TG1 was studied in chemostat cultures under non-selective (medium without antibiotics), selective (medium with β-lactam antibiotic ampicillin) and modified selective (medium with ampicillin and the β-lactamase inhibitor sulbactam) conditions. Under non-selective conditions, a behaviour typical of unstable systems was found. Under selective conditions, the behaviour predicted by the models was obtained – the fraction of plasmid-bearing cells in the population approached a constant value which was dependent on the ampicillin concentration in the feeding and on the cell concentration in the chemostat. Under modified selective conditions, the higher the concentration of sulbactam in the medium was, the higher the fraction of plasmid-bearing cells was in steady state conditions. |
