Re: Probability of evolving useful molecules
David Campbell (bivalve@mailserv0.isis.unc.edu)
Fri, 9 Jan 1998 13:36:43 -0400Related to the discussion of Yockey's book is a news article in the October
17, 1997 Science on colonies of E. coli grown under environmental
constraint for many years. Identical bacteria had initially been
introduced to one medium (glucose, I think) and had been given a long
period of time to get good at living on it. They were then introduced to
other media which normal E. coli do OK in. In the same new medium,
different bacteria did better or worse. This is believed to reflect
different mutations for better use of glucose-some of these mutations
impaired the ability to use other sugars, but all were good at using
glucose and related sugars.
There was also a good example of beneficial mutation, in a similar
setting. A soil bacterium was introduced to a sterile culture flask and
allowed to grow undisturbed. Different-looking colonies developed in
different parts of the flask; when samples from selected vaieties were
introduced to a new flask, they grew in specific parts of the flask, and a
low concentration of flask-bottom bacteria would outcompete a lot of middle
or top bacteria when placed in a low-oxygen (like the flask bottom)
environment. Middle and top colonies were similarly able to outcompete
when in their preferred environments.
David Campbell