Word: bacterium
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These natural transfers can be crucial to the survival of the bacterium. It is through new plasmids, for example, that bacteria like Staphylococcus aureus have become resistant to penicillin. The plasmid acquired by the staph bug contained a gene that directs the production of a penicillinase, an enzyme that cracks apart invading penicillin molecules, making them ineffective. Different plasmids, sometimes passed from one bacterium to another, can order up still another kind of chemical weapon, a so-called restriction enzyme, which can sever the DNA of an invading virus, say, at a predetermined point...
...coli did not merely accept the hybrid plasmids. When the bacteria reproduced-by dividing and thus doubling-at a rate of about once every 30 minutes, they created carbon copies of themselves, new plasmids and all. In only a day, one bacterium could make billions of duplicates of a transplanted gene...
...development of the recombinant DNA technique ushered in a new era of genetic engineering-with all of its promise and possible peril. The lowly organism that currently plays the largest role in the process is the E. coli bacterium. This microbe-a laboratory derivative of a common inhabitant of the human intestine-lends itself to being engineered because its genetic structure has been so well studied. In the first step of the process, scientists place the bacterium in a test tube with a detergent-like liquid. This dissolves the microbe's outer membrane, causing its DNA strands to spill...
...enzyme. This enzyme cuts through the plasmids' DNA strips at specific points. It leaves overlapping, mortise-type breaks with "sticky" ends. The opened plasmid loops are then mixed in a solution with genes-also removed by the use of restriction enzymes-from the DNA of a plant, animal, bacterium or virus. In the solution is another enzyme called a DNA ligase, which cements the foreign gene into place in the opening of the plasmids. The result of these unions are new loops of DNA called plasmid chimeras because, like the Chimera-the mythical lion-goat-serpent after which they...
...will fail-and that a few virulent bugs will slip through the safeguards to multiply in the outside world. Faced with this problem at the Asilomar conference. Geneticist Roy Curtiss III proposed an ingenious solution: Why not convert the standard genetic research organism, a strain of the E. coli bacterium, into a seriously weakened mutant variety that would quickly self-destruct if it escaped the laboratory? Curtiss volunteered to engineer the new bug, and his colleagues agreed to hold off on many of their recombinant DNA experiments until they could be supplied with...