Word: colis
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Finally, the chimeras are placed in a solution of cold calcium chloride containing normal E. coli bacteria. When the solution is suddenly heated, the membranes of the E. coli become permeable, allowing the plasmid chimeras to pass through and become part of the microbes' new genetic structure. When the E. coli reproduce, they create carbon copies of themselves, new plasmids -and DNA sequences-and all. Thus they become forms of life potentially different from what they had been before-imbued with characteristics dictated not only by their own E. coli genes but also by genes from an entirely different...
...someone 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...
Returning to his laboratory at the University of Alabama Medical Center in Birmingham, Curtiss quickly hit on a way to keep E. coli under control. The microbes must be able to manufacture a protective membrane; without such an outer coat they would swell and burst during normal growth. To keep them from manufacturing a complete coat, Curtiss created an E. coli with a defect in a gene that makes diaminopimelic acid (DAP), an important ingredient of the membrane. The defect made the bugs dependent for their survival upon DAP supplied by scientists...
After a few more genetic refinements, Curtiss had developed what seemed to be a safe research bacterium. But a major problem remained. Even dying E. coli bacteria can conjugate with healthy ones, transferring their possibly dangerous genetic material in the process. Thus an escaped and dying bug might still pose a danger. Again Curtiss worked his genetic magic, this time taking away from the microbe the ability to produce the chemical thymine, which is a component of the bug's own DNA. Without thymine supplied in the lab, the E. coli could not pass its genes on to healthy...
Curtiss named his transmuted bug E. coli x1776-in honor of the Bicentennial. In November 1976, the NIH certified it for use in genetic engineering experiments, removing one of the major obstacles to resuming recombinant DNA research...