Time-Resolved Plasmid Counting by Way of Transcription Factor Sequestration

Abstract

In contrast to the chromosome, genes expressed from plasmids exist in high copy number which changes continuously during the cell cycle. There are many models for how the control mechanisms associated with plasmid copy number dictate the cell-cycle dependent plasmid copy number, which have unique predictions for the dynamics of replication. We demonstrate a non-invasive method for dynamical quantification of plasmid copy number over the course of the cell cycle using the level of transcription from a reporter gene which shares a transcription factor with the plasmid. Using this method, we explore the cell-cycle dependent nature of plasmid replication for different origins of replication. Our method allows for discrimination of single-cell characteristics such as the single-cell division time and morphology and may permit discrimination of different replication mechanisms.

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