The ability of a bacterium to regulate the expression of the myriad of genes contained in the chromosome and plasmids is essential to the growth and survival of the microorganism. While a bacterium has many genes that code for a variety of proteins, these genes are not all expressed at the same time. Some genes are active all the time, while others are active only at specific times in the growth cycle of the bacterium or in response to a certain environmental condition. The amounts of proteins that are produced are not all the same. Moreover, the triggers that stimulate the expression of one gene can be quite different from the triggers for another gene. The ability of a prokaryotic cells (bacterial are the prototypical system) to orchestrate the expression of the repertoire of genes constitutes genetic regulation.

The activity...