Word: curtisses
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...labs; among other changes, it can no longer colonize in human or animal intestinal tracts. Biologist H. William Smith, an expert on infectious diseases in animals, suggests that the deliberate creation of an infectious E. coli K-12 would require 20 years. University of Alabama Geneticist Roy Curtiss III has developed an even more feeble strain. Back in 1974, Curtiss urged a halt to experiments designed to create new combinations of DNA in E. coli. Now Curtiss says research with the K-12 strain poses "no danger whatsoever...
Unfortunately, the defect proved insufficient. Some of the descendants of the new microbe mutated naturally and began manufacturing their own DAP. So Curtiss went a step further and deleted another gene involved in DAP production. These newly designed bugs remained DAPless. But more frustration awaited Curtiss: the mutants managed to survive and multiply even without DAP. How? Dennis Pereira, a graduate student who worked with Curtiss on the project, discovered that they were producing a sticky substance called colanic acid that held them together in the absence of their normal outer coat. By manipulating still another of the microbe...
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 is still working to develop a more perfect-or defective-microbe for recombinant DNA research. But for the time being, genetic engineers have available a tailor-made microbe that cannot survive outside the laboratory and that cannot colonize or even live in the human intestinal tract. Nor is this the only indication that the bug would make a poor pathogen, or disease organism. Curtiss' handmade microbe will not survive in human serum-including that of cancer patients. It is also easily destroyed by common household detergents...
...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...