Experimenting with evolution

Delft Outlook, July 2010

“Suppose you come face to face with a distant ancestor and must fight to find out who is stronger.” This proposition is raised by evolutionary biologist Dr Bertus Beaumont, who conducts experiments with bacteria.

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“Bacteria enable you to compare two very distant generations. I keep a suspension of bacteria in the freezer and let the rest of the colony evolve. It’s sometimes possible to move on eight generations in a single day. After a few hundred generations, I can compare the bacteria with their distant ancestors.” Bertus Beaumont (36) received his doctorate in molecular biology from VU University Amsterdam in 2004. He went on to work as a postdoc researcher at the University of Auckland and, with a NWO Veni research grant, under Professor Paul Brakefield at Leiden University.
“Everything we know about evolution we know through comparative research,” Beaumont states. Comparisons between fossils, comparisons between fossils and current life forms, and between existing species: the entire theory of evolution was developed on the basis of comparative observations. But scientists also like to conduct experiments to test their hypotheses. Current technology makes that possible, although patience and dedication remain essential given the number of successive generations required. Beaumont’s longest experiment involved studying 500 generations. In human terms, that would take 15,000 years, taking us back to the middle of the last Ice Age.
“I’m not concerned with showing that bacteria adapt to changing conditions,” Beaumont says. “We know that already. Rather, I am interested in how a complex mechanism such as a bacterium can adapt through random changes to its DNA. That is the real question.” The DNA of the bacteria used in his research has 6 million genetic letters. On each division, the DNA is copied, whereupon there is a 1 in 10,000 chance of a random mutation. Most mutations have no effect whatsoever. Some make the bacteria grow less quickly, whereupon the mutation itself eventually becomes extinct. Very occasionally, a bacterium will start to grow more quickly, whereupon the entire population eventually has the same characteristic. “In that case, they have evolved one step,” Beaumont summarises. In Delft, Dr Beaumont is to research the evolution of flagella. A flagellum is a sort of tail-like projection which certain bacteria have, and which they use to move around. It is rather like a tiny outboard motor. By studying only the mutations which affect the flagellum, Beaumont hopes to gain a greater understanding of the evolution of such biological nanomachines. He will also use that knowledge to make certain planned modifications. Evolution designs blind: a scientist likes to know what he is doing.