There doesn’t seem to be any end in sight. ~ American evolutionary biologist Richard Lenski on the perpetuation of evolution
Evolution is a restless dynamic, even in an unchanging environment. There always seems to be opportunity for creative adaptation.
American evolutionary biologist Richard Lenski stored E. coli bacteria in 4,000 vials of various sugary solutions. After 25 years and 58,000 generations (6.6 per day), still stuck in the simplest habitat, Lenski’s bacteria were still evolving.
The bacteria’s fitness improved rapidly early on; later slowing, but still going. Different colonies took distinct evolutionary paths.
In a single flask 2 different colony types evolved: one with small populations and relatively small cells, while another went for large cells in large populations. Domination of one type was expected. Instead, interactions between the different colony types created an ecosystem which allowed both to be viable: a win for pluck in negotiation.
Lenski put the bacteria on different media. One colony was running out of glucose, so it evolved to getting its energy from the citrate in the medium, allowing a much greater population density. Citrate is a citric acid derivative.
The citrate-consuming bacteria adapted by employing numerous genetic transformations. In the process, they speciated, as one of E. coli’s defining characteristics is not being able to use citrate as an energy source in the presence of oxygen.