Instability of the plasmid carrying active penicillin acylase gene from Escherichia coli: conditions inducing insertional inactivation

Abstract The marker instability of the recombinant plasmid coding penicillin acylase production was investigated in Escherichia coli . In the absence of any selective pressure and under fully induced production of penicillin acylase the number of cells lacking plasmids increased during cultivation. Cells still harboring plasmids fully maintained their ability to synthesize the enzyme. However, when a selection for Tet^r was applied, the number of selected cells containing the actively synthesizing gene decreased. Changes occurring in plasmid DNA revealed high frequency of insertions affecting expression of penicillin acylase gene.