Planet Earth

A Feast of Bugs

The LoomBy Carl ZimmerJun 26, 2007 9:03 AM


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In the past few months, the New York Times science section has been putting together some special packages of articles, and this week's bundle is on the topic of evolution. You can read John Noble Wilford on hominids, Nicholas Wade on recent human evolution, Carol Kaesuk Yoon on the evolution of animal development, and more. No animals for me, thanks--I got the microbes. Which is just fine with me. It's a world of evolution I get all to myself. In my article, I take a look at experiments in which scientists watch microbes evolve, testing out hypotheses about natural selection and other processes. I was already quite familiar with experiments on E. coli, which I learned about during the research for my next book on that particularly lovable species. But it was fascinating to get better acquainted with some of the many other experiments being carried out on other microbes, such as the soil predator Myxococcus xanthus. While E. coli may be good for studying a lot of features of biology, even I must admit that other species sometimes are the better pick. If you want to know how cooperation and cheating evolve, it only makes sense to look at microbes that actually hunt in packs, share their kills, and sacrifice their own lives so that their fellow M. xanthus can become spores and survive in times of famine. (The picture on the left is a spore-forming mound.) In the article, I focused mainly on basic questions in biology. Does evolution repeat itself, for example? How does biodiversity emerge? But these experiments are also meaningful to bio-engineers who manipulate microbes to churn out useful molecules like insulin or ethanol. Bernhard Palsson of UC San Diego ran an experiment in which E. coli adapted to a diet of glycerol. He was able to pinpoint all the mutations that natural selection favored in that process (something that hasn't been done before). Some of the genes they struck came as a complete surprise to him. He had no idea they could be important for breaking down glycerol. "We would never have had this knowledge by any other way," he told me. "This revolution is going to be a discovery tool." Here are a few of the key papers on which I based the article... Richard Lenski's long-term experiments: take your pick of pdfs from his web site. E. coli adapts to heatPalsson's glycerol experiment Social evolution in M. xanthus: abstract, pdfDiversification of Pseudomonas fluorescens

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