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Step by Step Speciation

Escherichia coli

Researchers at Michigan State University have performed an experiment detailing the step-by-step speciation of E. coli bacteria to consume citrate in the presence of oxygen.

The results show that new functions come about in three stages (generalizing from the specific experiment):

  1. Potentiation – mutation causing trait is acquired in population
  2. Actualization – trait caused by mutation is or becomes advantageous
  3. Refinement – mutations that enhance the new advantageous traits are acquired and propagate

Their research includes the frozen generations of e. coli so the exact situation and populations can be repeated.One interesting detail is that the mutation that enabled the consumption of citrate isn’t typical. Two chunks of DNA were combined so that one chunk encoded the new protein and the other expressed it.

The discovery of the mutant happened back in 2003. Years later have yielded much data as Carl Zimmer explains in his blog.

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