Evolution: Scientists Grow 56,000 Generations in Lab to Watch


"Zack showed you could re-evolve the citrate-eaters, but only after some of the other pieces of the puzzle were in place," Lenski said.

Some 29 genome sequences for the bacteria were carried out by the researchers, allowing them to pinpoint exactly when the various mutations occurred. Mutations were not unexpected, Blount said, because "they are going to occur as a matter of course because DNA replication is not completely accurate and that introduces some errors."

That's the way it happens throughout nature, not just among bacteria. With the exception of such things as chemical assaults and radiation, nature doesn't drive evolution. It's the other way around.

Mutations occur randomly, and usually do more harm than good, but occasionally they turn out to be beneficial to the organism. When it's beneficial, the organism will likely "select" the mutation and add it to its arsenal.

That's precisely what happened to the bacteria, although it took several mutations -- one to kick-start the process, another to get the ball rolling, and a third to take full advantage of the opportunity.

"These bacteria have evolved to consume a food resource -- citrate -- that no wild E. coli uses," said George Gilchrist, the National Science Foundation's program manager for the Michigan State project. "Three mutations (at least) were required for this to happen, and they must occur in a specific order."

He went on to say that the research suggests "complex traits, at least in the microbial world, can evolve quickly and repeatedly."

That still leaves at least one question dangling. Is the citrate-eating bacterium a new species? That's Blount's next challenge. And it won't be easy either.

"The question of what is or is not a species is a tangled one," he said. There literally are over 100 different species definitions."

But since the citrate eaters are doing something their kinfolk can't do, maybe they are a new species.

"This may be a chance to watch a new species forming from the very beginning," Blount said.

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