Through evolution, bacteria and other microorganisms can “learn” to anticipate a future environmental event and prepare for it, according to recent research from the Weizmann Institute, Tel Aviv University, and Harvard Medical School. The research findings showed that certain microorganisms' genetic networks are hard-wired to "foresee" what comes next in a normally predictable sequence of events and to begin responding to the new state of affairs before its onset. This is analogous to classical Pavlovian conditioning. As an example, E. coli bacteria, which normally cruise harmlessly down the human digestive tract, encounter a number of different environments on their way. In particular, they find that one type of sugar, lactose, is invariably followed by a second sugar, maltose, soon afterward. The research team checked the bacterium's genetic response to lactose, and found that, in addition to the genes that enable it to digest lactose, the gene network for utilizing maltose was partially activated. When the researchers switched the order of the sugars, giving the bacteria maltose first, there was no corresponding activation of lactose genes, implying that bacteria have naturally "learned" to get ready for maltose following lactose. In addition, when E. coli were raised in an environment containing the first sugar, lactose, but not the follow-up with maltose, the bacteria evolved, after several months, to stop activating their maltose genes at the taste of lactose, only turning them on when maltose was actually available. Senior author Dr. Yitzhak Pilpel and his team believe that genetic conditioned responses may be a widespread means of evolutionary adaptation that enhances survival in many organisms, and may also take place in the cells of higher organisms, including humans.
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