Control of Gene Expression in Bacteria by Induction

The regulation of gene expression is a basic
function of prokaryotic and eukaryotic organisms.
Prokaryotic organisms rely entirely on
their ability to adapt rapidly to changes in external
conditions. Substances usually present in
the nutrient medium need not be synthesized
by the bacterium itself. On the other hand, substances
not present must be synthesized by the
cell. The control of gene expression occurs at
different levels. Regulator proteins may act as
repressors (suppressing RNA polymerase activity)
or as activators (inducing RNA polymerase
activity). Control of prokaryotic genes is often
facilitated in that functionally related genes
usually lie together and therefore can be regulated
together