BBC Knowledge - April 2009 - (Page 42)
DAR DARW DARWIN Evolution in 200 ACTION collection asks R incubator. Aone holdingofa ﬂsplashsit inside, each ichard Lenski lifts the door of an Lenski has a hunch that they should no longer even be called E. coli. It’s going to take months to ﬁ nish the experiments he’s now running to see if he’s right. “At that point, I’d be conﬁdent to call it a new species,” he says. Lenski’s research shows just how far evolutionary biology has come since the days of Charles Darwin. Darwin did not run any experiments to observe evolution in action. He believed that it proceeded too slowly to be perceived by humans. Instead, he looked to the evidence of evolution’s effects that had accumulated over billions of years. But Darwin did live long enough to get a glimpse of an experiment in evolution. In 1878, a minister and amateur scientist named William Dallinger, from Liverpool, UK, wrote to Darwin to explain how he was raising microbes in a copper vessel of his own design. He could keep the water in the vessel at a constant temperature of his choosing. Over several months, he raised the water to 150oF (65.5oC), which instantly killed ordinary microbes. But Dallinger’s microbes thrived in the hot water. He argued that they had evolved adaptations to survive in the new environment. Along the way, the heatadapted microbes also became less suited to their previous way of life, and died when dunked in lukewarm water. Darwin praised the experiment in a letter to Dallinger: “Your results, I have no doubt, will be extremely curious and valuable.” Species don’t always take millions of years to adapt to a new way of life. Carl Zimmer meets the man who’s been watching evolution happen in his own professional lifetime, in his own laboratory of liquid. Lenski carefully takes one out, keeping his palm clamped tightly on the overturned beaker that serves as a lid. He spins the ﬂ ask as he inspects the sloshing liquid. “It’s a little cloudy,” he says, as though judging a ﬁ ne wine. “If you had a glass of water that colour, you wouldn’t want to drink it.” He puts the ﬂ ask back in the incubator and draws out another. “Now this one looks like you’ve mixed milk and water together,” he says. There’s a profound signiﬁcance in the colour of the two ﬂ asks, one that Lenski is studying to learn about the workings of evolution. Both ﬂ asks are loaded with Escherchi coli – a species of bacteria common to the human gut. Twenty-one years ago, Lenski used a single E. coli to establish 12 identical ‘lines’ of bacteria, each of which lived in its own ﬂ ask. Ever since the experiment started, the bacteria have been evolving. Lenski and his students and colleagues in his Michigan State University laboratory have been tracking the microorganisms’ evolution in ﬁ ne detail. Along the way, some of the bacteria have undergone extraordinary transformations. The microbes in the ﬂ ask Lenski is holding have experienced perhaps the most extraordinary change of all. They’ve evolved a new way of living, one that’s so successful that their population has exploded and turned their ﬂ ask cloudy. 42 Mar/Apr 2009
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