Genes microbial

Gene Expression Systems. One of the potentials of genetic engineering of microbes is production of large amounts of recombinant proteias (12,13). This is not a trivial task. Each proteia is unique and the stabiUty of the proteia varies depending on the host. Thus it is not feasible to have a single omnipotent microbial host for the production of all recombinant proteias. Rather, several microbial hosts have to be studied. Expression vectors have to be tailored to the microbe of choice. 

Other Microbial Systems. In addition to the systems described, gene cloning is routinely performed in several other bacterial strains including Streptoccocus Staphylococcus Brevibacterium BJdodobacter Comyebacterium Glucanobacter Acetobacter and Zanthomonas species. 

Resistance to Tetracyclines. The tetracyclines stiU provide inexpensive and effective treatment for several microbial infections, but the emergence of acquired resistance to this class of antibiotic has limited their clinical usehilness. Studies to define the molecular basis of resistance are underway so that derivatives having improved antibacterial spectra and less susceptibiUty to bacterial resistance may be developed. Tetracyclines are antibiotics of choice for relatively few human infections encountered in daily clinical practice (104), largely as a result of the emergence of acquired tetracycline-resistance among clinically important bacteria (88,105,106). Acquired resistance occurs when resistant strains emerge from previously sensitive bacterial populations by acquisition of resistance genes which usually reside in plasmids and/or transposons (88,106,107). Furthermore, resistance deterrninants contained in transposons spread to, and become estabUshed in, diverse bacterial species (106). 

Insulin is one of the important pharmaceutical products produced commercially by genetically engineered bactera. Before this development, commercial insulin was isolated from animal pancreatic tissue. Microbial insulin has been available since 1982. The human insulin gene is introduced into a bacterium like E. coli. Two of the major advantages of insulin production by microorganisms are that the resultant insulin is chemically identical to human insulin, and it can be produced in unlimited quantities. 

Microbial Resistance to Drugs. Figure 2 Bacterial cells can obtain resistance genes in three ways ... 

The discovery and exploitation of enzymes in aldoxime-nitrile pathway nitrile hydratase, amidase, nitrilase, aldoxime dehydratase, etc., are shown along with the use of methodologies, such as organic chemistry, microbial screening by enrichment and acclimation culture techniques, enzyme purification, gene cloning, molecular screening by polymerase chain reaction (PCR). 

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