New tool for metabolic pathway engineering in Escherichia coli: one-step method to modulate expression of chromosomal genes.

A simple and highly efficient method was developed to produce a library of Escherichia coli clones that express a particular chromosomal gene at a wide range of expression levels. The basic strategy was to replace all or part of the upstream region of a coding sequence containing the elements involved in its expression (promoter, operator, gene coding for a regulator, ribosome binding site, and start codon) with a PCR-generated library of expression cassettes.