Lenski's E. Coli: improve fitness without challenge (Introduction)

by David Turell , Thursday, December 17, 2015, 00:47 (3265 days ago) @ David Turell

The very long term E. coli experiment does not change the culture medium environment but the bacteria themselves improve 'fitness'.-http://www.the-scientist.com/?articles.view/articleNo/44787/title/Constant-Evolution/-"In a 2013 Science paper, researchers running the Long-Term Evolution Experiment (LTEE)—a project that has been monitoring 12 flasks of Escherichia coli for almost three decades—predicted that the bacteria would continue to adapt to their never-changing environment forever. Now, two years and 10,000 bacterial generations on, it's clear that their prediction is holding true. The team's latest report, published in Proceedings of the Royal Society B today (December 16), shows that the fitness of the bacterial populations is indeed continuing to improve.-***-"In 1988, evolutionary biologist Richard Lenski of Michigan State University initiated the LTEE. His team divided one starter culture of E. coli into 12 separate flasks and, for the last 27 years, those 12 cultures have been kept in identical conditions, being diluted by a factor of 100—to allow for growth—with the same culture medium each and every day.-"The aim was to investigate “the predictability and repeatability of the evolutionary process,” said study coauthor Michael Wiser, also of Michigan State University. Put simply, “the idea was to look and see whether the different populations were achieving the same results as each other and whether they were doing so at the same time,” he said.-"As the years passed, the team collected and froze sample after sample, performing various analyses on each. Once the bacteria reached 50,000 generations, the researchers compared the fitness of the then-current cultures with that of the microbes' predecessors and their common ancestor. The researchers found that fitness was improving."-Comment: The mechanism to evolve is built-in to living organisms.