Bacteria as Protein Factories

We can use the reproductive power of bacteria to express large quantities of a mammalian protein of interest however, the process is often more complicated than it might seem because most mammalian proteins are heavily processed after their initial transcription and translation (Section 12.7). Because bacteria have little posttranslational modification of their proteins, they lack the enzymes necessary for this processing. 

Increased milk production. Much controversy exists over providing cows with supplemental bovine somatotropin (BST), also called growth hormone, a hormone that increases metabolism and milk production in dairy cows. Tbe controversy centers on human consumption of the hormone. However, BST is a peptide hormone, so it is hydrolyzed in the digestive tract and is not absorbed directly into the human bloodstream (Section 24.2). Furthermore, aU milk must contain some of this hormone, because the cow cannot produce milk without it. A more soundly based concern about BST supplementation in dairy cows is that the cows given extra BST often develop mastitis, an inflammation of the udder caused by bacterial infection. Mastitis is frequently treated with high doses of antibiotics, and some of these antibiotics could end up in tbe mUk, causing problems for people with certain food sensitivity. 

Good predator attraction. Researchers in the Netherlands were studying the mustard plant, AraMdopsis thaliana, which is very susceptible to attack by herbivorous spider mite predators. They introduced a strawberry gene into the mustard plants that produces a chemical attractant for predatory mites that eat the herbivorous spider mites. 

Researchers created a transgenic version of the mustard plant, Arabidopsis thaliana, that contained a strawberry gene that produces an attractant for predatory mites that will eat herbivorous spider mites (shown in inset). (Photos cmirtesy of Marcel Dicke — Wageningen University — The Netherlands — www.ent.umr.nl) 

---