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Gene travel: plasmids around the world.

Gene travel: Plasmids around the world

Genetic engineers have taken advantage of the processes by which bacteria naturally exchange genes. One concern about the environmental release of genetically engineered bacteria is that any foreign genes that scientists have added to a microorganism might be transferred on mobile pieces of DNA, called plasmids and transposons, to other bacteria in the surroundings, with unforeseen adverse consequences. Studies of hospital patients, for example, reveal that the same plasmid or transposon, carrying a natural gene making the bacteria resistant to an antibiotic, can be found in patients across the United States and in distant nations. Some biologists suggest that the rate of bacterial gene exchange is so great that scientists must simply assume that any gene introduced into one species of bacterium will soon be found in all.

The exchange of genes is not limited to bacteria colonizing the gut of a single animal species. Start B. Levy of Tufts University School of Medicine in Boston and his colleagues previously demonstrated spread of plasmids from bacteria in chickens to those in people. They now add evidence that genes can also spread from bacteria colonizing the human gut to those of other animals.

The scientists recently examined bacteria in the feces of yellow baboons in a national park in Kenya. The groups of baboons that had little contact with people were about 10 percent as likely to carry bacteria resistant to antibiotics as was a group of baboons whose range included a tourist lodge, with its refuse dumps and latrines. Even though the animals were probably not exposed to any antibiotics, almost all the "lodge' baboons, but few of the free-living baboons, harbored bacteria resistant to two to four different antibiotics.

"Our findings implicate food wastes and other forms of refuse as sources of resistant nonpathogenic bacteria in the intestine,' Levy and his collaborators wrote in the April APPLIED AND ENVIRONMENTAL MICROBIOLOGY. "Moreover, these data call attention to a previously unrecognized pathway by which antibiotic-resistance plasmids may be transmitted to wild animals and subsequently spread to the natural environment.'
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Title Annotation:bacterial gene exchange
Author:Miller, Julie Ann
Publication:Science News
Date:Jun 29, 1985
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