::::The development of citrate metabolizers wasn't the main intent (see Lenski's early papers) and it's actually tangential in the overall context of the long-term experiment. Zachary Blount describes the purpose of citrate in the media in his responses at Carl Zimmer's blog, The Loom. http://scienceblogs.com/loom/2008/06/02/a_new_step_in_evolution.php (see replies #115 & #270). Citrate was not added to be a carbon nutrient in the media but as a non-metabolizable chelator (the three carboxyl groups of citrate can bind certain cations in solution). The recipe for the medium was taken from other microbiologists who developed the recipe as a general culture medium back in 1949. Lenski's description of the DM25 media is here: https://myxo.css.msu.edu/ecoli/dm25liquid.html. Glucose was the intended carbon source. If you read the Lenski article cited by Blount (Phenotypic and genomic evolution during a 20,000-generation experiment with the bacterium Escherichia coli. -- available here: https://www.msu.edu/~lenski/, you'll see the setup and reasons for performing the experiments (An earlier article at generation 2000 is here: http://myxo.css.msu.edu/lenski/pdf/1991,%20AmNat,%20Lenski%20et%20al.pdf). Basically, Lenksi wanted to see how mutations arise and move through populations over time. Even if the media and growth conditions remain pretty consistent over time, the populations continuously shift and change. That is because for a bacterium in the experiment the 'environment' is not just made up of the flask and media but also the *other cells in the flask* with which it must compete. This results in a continuously shifting competitive environment as mutations arise in lineages. Citrate utilization was just one of the many interesting variations acquired over the course of the experiment. Read his other papers for more details and a fuller understanding of the open-ended experiment's scope.--[[User:Argon|Argon]] 21:16, 26 June 2008 (EDT) | ::::The development of citrate metabolizers wasn't the main intent (see Lenski's early papers) and it's actually tangential in the overall context of the long-term experiment. Zachary Blount describes the purpose of citrate in the media in his responses at Carl Zimmer's blog, The Loom. http://scienceblogs.com/loom/2008/06/02/a_new_step_in_evolution.php (see replies #115 & #270). Citrate was not added to be a carbon nutrient in the media but as a non-metabolizable chelator (the three carboxyl groups of citrate can bind certain cations in solution). The recipe for the medium was taken from other microbiologists who developed the recipe as a general culture medium back in 1949. Lenski's description of the DM25 media is here: https://myxo.css.msu.edu/ecoli/dm25liquid.html. Glucose was the intended carbon source. If you read the Lenski article cited by Blount (Phenotypic and genomic evolution during a 20,000-generation experiment with the bacterium Escherichia coli. -- available here: https://www.msu.edu/~lenski/, you'll see the setup and reasons for performing the experiments (An earlier article at generation 2000 is here: http://myxo.css.msu.edu/lenski/pdf/1991,%20AmNat,%20Lenski%20et%20al.pdf). Basically, Lenksi wanted to see how mutations arise and move through populations over time. Even if the media and growth conditions remain pretty consistent over time, the populations continuously shift and change. That is because for a bacterium in the experiment the 'environment' is not just made up of the flask and media but also the *other cells in the flask* with which it must compete. This results in a continuously shifting competitive environment as mutations arise in lineages. Citrate utilization was just one of the many interesting variations acquired over the course of the experiment. Read his other papers for more details and a fuller understanding of the open-ended experiment's scope.--[[User:Argon|Argon]] 21:16, 26 June 2008 (EDT) |