LOS ANGELES, April 27 (Xinhuanet)-- US researchers reported on Wednesday they have successfully programmed bacteria to communicate with each other and produce color-coded patterns, making living cells function as "tiny computers."

    This achievement will finally help manipulate living cells to detect hazards, build structures or repair tissues and organs within the body, said researchers at Princeton University. Their work is published in the April 28 issue of journal Nature.

    "We are really moving beyond the ability to program individual cells to programming a large collection -- millions or billions --of cells to do interesting things," said Ron Weiss, an assistant professor at Princeton University who led the study.

    The researchers programmed E. coli bacteria to emit red or green fluorescent light in response to a signal emitted from another set of E. coli. In one experiment, the cells glowed green when they sensed a higher concentration of the signal chemical andred when they sensed a lower concentration.

    The bacteria formed a bull's-eye pattern, a green circle insidea red one surrounding the sender cells, in a Petri dish. This sensing system could be useful for the detection of chemicals or organisms in laboratory tests.

    "The bull's-eye could tell you this is where the anthrax is," Weiss said.

    In previous work, Weiss showed the feasibility of inserting modified pieces of DNA into cells to make them behave in the same manner as digital circuits. The cells could be made to perform basic mathematical logic and produce crisp, reliable readouts thatare more commonly associated with silicon chips than biological organisms.

    The new study applied similar techniques to a large population of cells, showing an integrated package where the cells have an ability to send messages and other cells have the ability to act on these messages, according to Weiss.

    The creation of patterns, such as the bull's-eye effect, is a key step to have the cells secrete materials that build physical devices such as antennas or transmitters in places that are hard for humans to reach.

    Programmed cells also could be used to control the repair or construction of tissues within the body, possibly guiding stem cells to the locations where they are needed for the growth of newnerve or bone cells in a process called "programmed tissue engineering."

    Even the early step of creating patterns in a Petri dish may beuseful as a tool for other scientists, particularly developmental biologists who are trying to understand how the cells of an embryoarrange themselves into patterns that become the various body parts of a mature organism.

    In fruit fly embryos, for example, the first cells are thought to differentiate into the head, abdomen and other parts based on the concentration of chemical signals that are emitted from the ends of the embryo.

    "Construction and study of such synthetic multicellular systemscan improve our quantitative understanding of naturally occurring developmental processes and may foster applications in tissue engineering, biomaterial fabrication and biosensing," the researchers said in their paper. Enditem