Answer by Diane Eager
What is the Lenski Experiment?
In 1988 Richard Lenski and his team at Michigan State University began culturing bacteria named E. coli in a medium containing the sugar glucose and a natural food acid named citrate. Normally E. coli do not use eat citrate when oxygen is present in the environment they are growing in. After 31,500 generations Lenski found one culture of E. coli was able to eat citrate when oxygen was present. This has been claimed to be proof that bacteria have evolved a new function and that useful information can be generated by naturalistic processes. The experiment was reported an article entitled: Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli Zachary D. Blount, Christina Z. Borland, and Richard E. Lenski Proceedings of the National Academy of Sciences (PNAS) doi: 10.1073/pnas.0803151105 PNAS June 10, 2008, vol. 105 no. 23 7899-7906.
Evolution in Action?
According to Richard Dawkins, “the Lenski experiments are distressing to creationists, and for a very good reason. They are a beautiful demonstration of evolution in action.” (Richard Dawkins, The Greatest Show on Earth, Bantam Press, 2009, p117) E coli was first classified in 1885 and using all the criteria used at that time, any claimed change is still regarded as so insignificant that E. coli is still classified as the same species of bacteria, i.e. E. coli. For all practical purposes the bacteria have multiplied after their kind for many thousands of generations, which is what creationists claim they were made to do. Lenski’s bacteria are still the same species after twenty years of sub-culturing. So what has changed? How have they changed, and is it even micro-evolution?
How did it happen?
It may come as a surprise but E. coli did not need to evolve a whole new chemical pathway to eat citrate. They already had a biochemical pathway to use citrate as an energy source, but it normally works only when the bacteria are growing in anaerobic (non-oxygen) conditions. The change in Lenski’s bacteria was that they could now use it in aerobic (oxygen present) conditions. Lenski’s research team provided a clue as to what happened. They wrote: “What physiological mechanism has evolved that allows aerobic growth on citrate? E. coli should be able to use citrate as an energy source after it enters the cell, but it lacks a citrate transporter that functions in an oxygen-rich environment.” PNAS, vol. 105 pp7899-7906, 10 June 2008
Having asked how the change could occur, Lenski comes up with two possible answers: “… an existing transporter has been coopted for citrate transport under oxic conditions. This transporter may previously have transported citrate under anoxic conditions or, alternatively, it may have transported another substrate in the presence of oxygen. The evolved changes might involve gene regulation, protein structure, or both.” PNAS June 10, 2008, vol. 105 no. 23 7899-7906 Let’s take up Lenski’s two suggestions and see if they involve evolution.
The bacteria could use citrate in aerobic conditions if a gene regulator that normally turns on the citrate transporter only in anaerobic (non-oxygen) conditions now losses a control function and now turns the citrate transporter on all the time. This is the equivalent of a door being jammed opened all the time so that it ceases to be a means of controlling what comes into the cell under different conditions. This however is a loss of function, i.e. degeneration, caused by the loss or disruption of genetic information. It is not a gain in complexity. It is not a gain in new information and neither is it a gain of a new function, so therefore it is change, but it is not evolution!
Alternate Protein Transporter
Checking Lenski’s second suggestion, we find that nutrients are transported into cells by large proteins that have a three dimensional structure that precisely fit certain molecules. It is very possible that a transport protein originally used for tartrate, a molecule with very similar structure to citrate, can now be slightly misshapen due to a mutation in the gene for its structure and can now transport both tartrate and citrate. This loss of a precise three dimensional structure, so that it no longer specific just for the tartrate shape, is also a decrease in function, and therefore, is also not evolution.
We don’t like to disappoint Richard Dawkins, but rather than being stressed about Lenski’s experiment, we are very interested in suggestions that change has occurred by degeneration and mutations, so we will watch for more reports. They should provide a good opportunity to learn more about how bacteria work, and how they can devolve. Furthermore, this experiment started with fully functional bacteria and seems to have produced degenerate mutants. Since this fits well into the Biblical history of the world, which tells us the living things were created as complete, fully functional organisms, but have lost functions as the world has degenerated due to human sin and God’s judgement, again we have to to disappoint dear Richard. Rather than being evidence for evolution, the Lenski experiments are providing evidence for creation.
Were you helped by this answer? If so, consider making a donation so we can keep adding more answers. Donate here.