Location and dynamics of an active promoter in Escherichia coli K-12

In the present paper, we report that transcription affects the location of a DNA target in Escherichia coli K-12. A strain whose chromosome had been engineered to encode a lac repressor–GFP (green fluorescent protein) fusion was used as a host for a low copy number plasmid that carries an array of five lac operator sites. Individual cells of this strain exhibited a diffuse fluorescence signal, suggesting that the plasmid is distributed throughout the cell cytoplasm. However, a derivative of this plasmid carrying a cloned constitutive promoter is targeted to a location at the edge of the nucleoid towards the pole of the host cell. We conclude that transcription from the cloned promoter is driving the location of the plasmid and that specific locations in bacterial cells may favour gene expression.