Live & let live
bacteria have been genetically modified to act as drugs within human bodies. The organisms are designed to treat inflammatory bowel disease by producing a human immune protein that dampens inflammation. gm bacteria are widely used to make food and drugs; but the prospect of drug-producing gut bugs getting into the wrong people or swapping genes with other bacteria has been the concern of many. To address such fears, the bugs have now been altered so that they die within days when discharged into the environment along with faeces.
For now, the 12 patients at the Academic Medical Centre, Holland, who have been administered the bacteria, are being kept in isolation. "They can't go out, and all their faeces are collected and then destroyed,' says Lothar Steidler, a scientists at the uk-based University of Cork, who heads the group pioneering the therapy.
Steidler's team chose the Lactococcus lactis bacterium because tonnes of it are already consumed in dairy products such as cheese. But rather than simply adding an extra gene to the bacterium, a gene producing the human immune protein (interleukin-10) was used to replace a key bacterial gene called the thy a. This codes for the enzyme needed to make thymidine, one of the building blocks of the bacterium's dna.
In the gut, thymidine is released as food is digested; therefore the modified bugs can flourish there even though they cannot make the enzyme. But outside the gut, where there is little thymidine available, the bacteria die, as Steidler's team has shown in experiments on mice and pigs. It is also highly unlikely that the bacterium will acquire a copy of thy a from other bacteria, as the gene is found on the main bacterial chromosome, rather than one of the smaller pieces of dna called plasmids that bacteria swap freely.
Patients take the bacteria as a coated pill that protects the bugs in the stomach till it breaks open and ejects its live cargo in the small intestine and colon. But it remains to be seen if the treatment will work or not
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