Plasmids, multicopy

FIGURE 5.3.5 Enhancement of lycopene accumulation in . coZi by over-expression of DXS. Lycopene accumulation (left) is enhanced (right) when E. coli cells carrying a carotenoid pathway gene cassette (+EIB) are further transformed with a dxs gene on a multicopy plasmid (+E1B +dxs). Lycopene hyperaccumulation was demonstrated by Matthews and Wurtzel. ... 

Since the reaction doesn t require accessory protein factors and can be performed in vitro with a variety of DNA substrates, the Cre-loxP system is much used in genetic engineering.583 584 A pair of related integrase subunits known as XerC and XerD perform a similar function for the E. coli chromosome as well as for multicopy plasmids.585 586 The XerC / XerD system is... 

Multicopy plasmids offer a limited, but still instructive comparison. Plasmids are replicating clusters of genes in bacteria. Under certain conditions they confer beneficial traits (such as resistance against antibiotics) on the bacterial host. They can also be passed on by conjugation between cells. A well elucidated mechanism of copy number control of abundant plasmids relies on a frans-acting inhibitor and czs-acting activator. For example, the ColE 1 plasmid in Escherichia coli blocks the action of the RNA primer (activator) by... 

Plasmid An extrachromosomal circle of DNA found in bacteria and yeast that can confer antibiotic resistance to a bacterial host and can be transferred from one cell to another. Capable of self-replicating and can exist in multicopy numbers within a cell. Used as the main vector for gene cloning. 

Multicopy plasmids containing the Z. mobilis pyruvate decarboxylase gene was inserted into K. planticola. The transformant was shown to produce 31.6 g/1 ethanol from a mixture of sugars (79.6 g/1) that included xylose [102]. The yield of acids (formic, acetic, lactic) and butanediol was reduced significantly. 

The cloning of the aspA gene onto the multicopy plasmid pBR322 [29] led to a modest fourfold to sixfold overproduction of aspartase compared with host strain without the clone [24]. The aspartase activity of the clone was further enhanced by deregulation of the gene using the lactose inducible, tac promoter [30,31]. The resultant plasmid (pPT174), when fully induced, produced 190-fold more aspartase activity than the E. coli K12 parental strain without the plasmid [31],... 

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