Plasmids for Independently Tunable, Low-Noise Expression of Two Genes.

Some microbiology experiments and biotechnology applications can be improved if it is possible to tune the expression of two different genes at the same time with cell-to-cell variation at or below the level of genes constitutively expressed from the chromosome (the "extrinsic noise limit"). This was recently achieved for a single gene by exploiting negative autoregulation by the tetracycline repressor (TetR) and bicistronic gene expression to reduce gene expression noise. We report new plasmids that use the same principles to achieve simultaneous, low-noise expression for two genes in The TetR system was moved to a compatible plasmid backbone, and a system based on the repressor (LacI) was found to also exhibit gene expression noise below the extrinsic noise limit.