Abstract: The present invention relates to methods of selecting for highly productive clones of E. coli for the production of plasmid DNA comprising measuring the frequency of IS1 transposon insertional mutagenesis within either the plasmid or genomic DNA of transformed clonal subtypes. An increase in IS1 insertional mutagenesis is correlated with clonal subtypes likely to exhibit a low specific productivity. The PCR-based, genetic selection assays disclosed herein are amenable to high throughput analysis, reducing the time to identify highly productive clones capable of cultivating large quantities of plasmid DNA on an industrial scale.