Richard E. Lenski expected his experiment to last maybe a year when he put E. coli bacteria into a culture of glucose and citrate to watch it evolve over the course of generations.
Studies of evolution traditionally have focused on fossils and comparative anatomy. But this offered a chance to witness it in real time, generation after generation, genetic mutation by mutation, how a harmless species of the infectious bacteria progressed and adapted.
"There is so much evidence of how evolution works, with fossils and the tree of life and the DNA of organisms, that I had no doubts that evolution works as the theory is understood," the Michigan State University evolutionary biologist said. "But I opted to look at the details that are difficult to see in nature."
Twenty-six years and nearly 60,000 generations after the project was launched, on today's date in 1988, Mr. Lenski continues the experiment. The dogged research project now provides many thousands of generations of frozen bacteria. He's drawn international attention and praise for providing hard evidence of how the E. coli used Darwinian principles to evolve into larger, more adaptive organisms that reproduce more rapidly.
It's the nuts and bolts of evolution, revealing that evolution occurs even faster than Charles Darwin and others had thought. It also reveals that evolution never ceases even in an unchanging environment of the solution. When frozen samples of previous generations are allowed to resume regeneration, the evolutionary process tends to replicate itself, countering traditional thinking that evolution might follow a divergent path if given a second chance.
"I didn't plan an ending," Mr. Lenski said, noting that it will continue indefinitely. "I stepped back to see what happened, and now I say that the experiment just keeps on giving."
He will present Duquesne University's 2014 Darwin Day lecture at 7 p.m. Wednesday in the university Power Center ballroom. Darwin Day is an annual, international celebration of the life and work of Darwin, whose 1859 publication "The Origin of Species" shocked the world with the now scientifically accepted theory that organisms evolved into current states of being.
"People who don't understand evolution often comment that you can't see evolution happening," said David Lampe, associate professor of biology at Duquesne and Darwin Day organizer. "Dr. Lenski's experiments have produced one of the best real-time evolution data-sets in existence. He can see evolution at work in real time and, coupled with the ability to freeze and revive organisms, he can also travel back in time, which is unique."
Over the past quarter century, the original 12 experimental populations of Escherichia coli bacteria have evolved rather dramatically but consistently. Their size has increased by 50 to 100 percent compared with original ancestors, while reproducing significantly faster by a similar percentage. Random mutations can weaken a bacterium and lead to its demise. But other mutations, or combinations thereof, allow development of new traits that enhance survivability and adaptation to changing environments. It exemplifies survival of the fittest, among other Darwinian principles.
One of the more dramatic developments occurred with about the 30,000th generation, when one of the 12 populations of E. coli began consuming citrate in the solution -- a food source the bacteria previously didn't consume. It's possible that the population represents a new species of E. coli.
"We joked that the bacteria went to bed and left the dessert uneaten every night for 15 years, and one population discovered a second source of energy in the medium," Mr. Lenski said.
The team freezes specimens every 500 generations -- about once every 75 days. Those samples are available for research. Development of genome sequencing technology now allows more thorough examination of DNA in successive generations to reveal evolution occurring mutation by mutation. One report suggests that the nearly 60,000 generations of E. coli would be equivalent to a million years of human evolution.
Mr. Lenski said he continues consulting in projects that employ evolutionary principles to improve technology. Roboticists, for example, are using self-replicating and ever-mutating computer programs that compete for computer time by using random mutations to develop more beneficial computer processes and skills. The improved programs are then used to operate robots.
Simply put, robots now are evolving.
"Many labs already are using evolutionary principles to work in context with robots," Mr. Lenski said.
David Templeton: firstname.lastname@example.org or 412-263-1578.