NOVELTY - Identifying a cell with increased production of a desired product comprises providing a population of cells which produce the desired product; and introducing distinct nucleic acid molecule species into the population of cells, where the nucleic acid molecules comprise a first region which is operably-linked to a second region, where the first region comprises a promoter region from a first gene, and the second region comprises a nucleic acid sequence from a second gene that is capable of expressing a regulatory product under control of the promoter region.    USE - The methods are used for identifying a cell with increased production of a desired product; producing a cell with increased production of a desired product; producing a desired product; increasing the production of a desired product; and bioremediation of a waste product (all claimed).    ADVANTAGE - The cell is used for increased, low cost, rapid and improved production of a desired product.    DETAILED DESCRIPTION - Identifying a cell with increased production of a desired product comprises (a) providing a population of cells which produce the desired product; (b) introducing distinct nucleic acid molecule species into the population of cells, where the nucleic acid molecules comprise a first region which is operably-linked to a second region, where the first region comprises a promoter region from a first gene, and the second region comprises a nucleic acid sequence from a second gene that is capable of expressing a regulatory product under control of the promoter region; (c) culturing the population of cells under conditions in which the cells express the regulatory product under control of the promoter region; and (d) testing the population of cells for production of the desired product, thus to identify a cell or cells with increased production of the desired product. INDEPENDENT CLAIMS are:    (1) a method of producing a cell with increased production of a desired product by providing a cell which produces a desired product; and introducing into the cell a nucleic acid molecule described above;    (2) a method of producing a desired product by culturing a cell with increased production of the desired product that has been produced, identified or isolated according to the method above, or its descendants with increased production of the desired product, under conditions in which the cell expresses the desired product;    (3) a cell produced by, identified by, or isolated by the method above, or its descendant, with increased production of the desired product;    (4) a method for increasing the production of a desired product by producing, identifying, or isolating, by the method above, cells with increased production of the desired product; culturing the cells, or its descendants with increased production of the desired product, under conditions in which the cells express the desired product; and recovering the increased amount of the desired product from the cells or the cell culture;    (5) a method for bioremediation of a waste product by providing cells produced by, identified by, or isolated by the method above, or its descendants, with increased production of a desired product that metabolizes the waste product; and exposing the cells to the selected waste product, thus providing bioremediation of the selected waste product;    (6) a collection of cells that produce a desired product, where the cells in the collection comprise distinct nucleic acid molecule species, where each nucleic acid molecule comprises a first region which is operably linked to a second region, where the first region comprises a promoter region from a first gene, and the second region comprises a nucleic acid sequence from a second gene that is capable of expressing a regulatory product under control of the promoter region, and where the desired product is not green fluorescent protein (GFP); and    (7) a kit of parts comprising a population of cells that produce a desired product; and distinct nucleic acid molecule species, where each nucleic acid molecule comprises a first region which is operably linked to a second region, where the first region comprises a promoter region from a first gene, and the second region comprises a nucleic acid sequence from a second gene that is capable of expressing a regulatory product under control of the promoter region in the cells that produce the desired product.