| home | subscribe | jobs | LATEST NEWS Worst nightmare Terrorists could easily make an atomic bomb from MOX fuel, says a confidential report Tagged for death Abnormalities found in the DNA of cloned embryos could explain why so many die Dead heat Heat and high levels of carbon monoxide seriously impair racing drivers' performance First among equals New techniques are making the Gnutella file-sharing network flourish, but may also dent some key benefits Current champion The bright new hope of superconductors overtakes its rivals on the amount of current carried Stemming research A lawsuit against the US government could be crucial in the search for medical therapies based on embryonic stem cells Occupational hazard Sports injuries don't just affect athletes - furry-costumed mascots are also highly susceptible Home from home An endless stream of other people's home movies will soon be beamed directly into your home Under wraps NASA must start planning a quarantine facility for Martian samples now, says an expert panel Inside job Doctors perform the first heart bypass that does not require open-heart surgery Watching worm A new computer worm that seeks out and reports child pornography is criticised for being too unsubtle Serious setback Fresh cases of foot and mouth disease in the UK are raising fears that the outbreak is far from over Sex change The anti-impotence drug Viagra works for young women as well as men, according to Italian research Living logic GM bugs that do the same job as the components of a microchip are revealed in the US Fatal feed HIV-infected mothers who breastfeed have much higher death rates than those using formula milk Prying eyes A report on the global spy network Echelon recommends all Europeans use encryption and open source software Deep impact A $279 million pot shot aimed at blasting a hole in the surface of a comet gets the go-ahead Cyanide death A new suspect for the mysterious deaths of over 500 thoroughbred foals in Kentucky emerges - cyanide Double whammy The idea that multiple sclerosis is triggered by two separate viruses receives a boost Poison spill Environmental officials are waiting to see if a rat poison spill on the New Zealand coast poses a threat to whales Small and smart Modern mammals owe much of their success to the tiny size of their Jurassic ancestors Daily News Archive Living logic GM bugs that do the same job as the components of a microchip are revealed in the US Exclusive from New Scientist magazine Genetically engineered bugs that do the same job as the components of a microchip have been created by a US team. These smart bugs will crunch on chemical inputs rather than digital bits. They could one day be sent into waste-water plants to hunt out toxic chemicals. Or they could tell doctors what proteins are present in body fluids. Just like a silicon-based AND gate that requires two electrical inputs, the bacterial logic gate will only produce an output when both its chemical inputs are present. It is the combination of such simple functions that allows computers to perform highly complex tasks, says Michael Simpson, a physicist at the Oak Ridge National Laboratory in Tennessee. But PCs with living logic circuits are still a long way off, warns Tim Gardner, a bioengineer and president of Cellicon Biotechnologies in Boston. For one thing, the basic components are not as good as silicon. "They are slower, noisier and more difficult to manipulate," he says. Complex gates Nature already combines simple functions to good effect, says Simpson. "When you look at genetic circuits you see things that look like binary logic and feedback patterns." The challenge is to manipulate them to your advantage. So Simpson, together with Gary Sayler and James Fleming, modified Pseudomonas putida cells to produce both AND and OR gates (see Graphic). They are now trying to produce more complex gates. The trick, he says, is to choose the genes to suit the kind of inputs and outputs you want. In the case of the AND gate, for example, they used chemical "inducers" as inputs. One causes a gene to make a protein that the second input inducer must have to express the output enzyme. You need both inducers to produce an output, which could, for example, be a bioluminescent enzyme. Normal metabolism Simpson is optimistic about the future of bug-based chips. "We're trying to take advantage of what cells do well - processing information on the molecular scale," he says. With the right sequence of inputs and outputs, you could have a number of gates inside a single cell, with the output of one gate becoming an input of another. In theory, a single cell could produce massively parallel complex functions. Because the chemical inputs don't alter the normal control metabolism, the cells can still reproduce and survive. But in a competitive environment with other unmodified cells they would be at a disadvantage, says Simpson, as they would be expending energy on computations instead of survival. Correspondence about this story should be directed to letters@newscientist.com 1900 GMT, 23 May 2001 Duncan Graham-Rowe New Scientist Online News Sign up for our free newsletter Subscribe to New Scientist New Scientist Home _________________________ NEW SCIENTIST Contents page New Scientist Jobs Graduate CareersEditorial News Features Opinion Letters Feedback The Last Word Back Issues _________________________ WEB ONLY: Insight Special Reports Bizarre Science Last Word Q & A Archive Web Links & Site of the Day Science Books Artspace _________________________ Search the site _________________________ Subscribe © Copyright New Scientist, RBI Limited 2001