SkipCaptcha
212
edits
Changes
Jump to navigation
Jump to search
Line 288:
Line 288: − + +
Conservapedia talk:Lenski dialog (view source)
Revision as of 03:26, June 30, 2008
, 03:26, June 30, 2008no edit summary
::::That statement is too vague.
::::That statement is too vague.
::::''"The glucose cycling does not inherently favor the development of a Cit+ strain any more than it favors other potential solutions to the problem - like secreting a toxin to kill your competitors, or faster reproduction to outbreed them, or photosynthesis, or cannibalism, or what have you."''
::::''"The glucose cycling does not inherently favor the development of a Cit+ strain any more than it favors other potential solutions to the problem - like secreting a toxin to kill your competitors, or faster reproduction to outbreed them, or photosynthesis, or cannibalism, or what have you."''
::::The glucose cycling gives an especially big advantage to Cit+ bacteria because they have something to eat after the glucose supply is exhausted whereas their Cit- neighbors do not.
::::The glucose cycling gives an especially big advantage to Cit+ bacteria because they have something to eat after the glucose supply is exhausted whereas their Cit- neighbors do not.
:::::It gives them '''an''' advantage. It's impossible to predict ahead of time how '''big''' an advantage it is, because instead of being unable to metabolize citrate they may merely be terrible at it. If the Cit- cells are better at glucose metabolism than the Cit+ ones are, they may completely swamp out the Cit+ in the early, glucose-dependent phase. Even if the Cit+ cells continue to grow after the glucose is exhausted, they may never completely outcompete the Cit- cells by the time the next population sample is taken. In fact, this appears to be what has happened, as the experiment has shown that two populations of cells originating from the Ara-3 line have reached a temporary equilibrium: a grows-very-fast-on-glucose Cit- population (10%) and a grows-more-slowly-on-glucose-but-keeps-growing-on-citrate Cit+ population (90%). Using the island analogy: the Cit- folks can eat a candy bar and divide in half a day rather than a day. The Cit+ folks can eat a candy bar and divide once a day, and once the candy bars are gone they can eat the wrappers and divide every day and a half. Now it's just the timing of the helicopter ride that determines whether there are more Cit+ or Cit- people carried to the next island. If the helicopter comes quickly, the Cit- will be favored. If it comes late, the Cit+ will be favored.--[[User:Brossa|Brossa]] 23:26, 29 June 2008 (EDT)
::::''"Citrate is present in the growth medium as a chelating agent and buffer -- it was not added solely to serve as a potential carbon source, although it is one."''
::::''"Citrate is present in the growth medium as a chelating agent and buffer -- it was not added solely to serve as a potential carbon source, although it is one."''
::::Yes, I know it is there as a chelating agent -- but I also want to know if Cit+ evolution was a goal (again, a goal does not have to be an expected result and can even be an unlikely result) and if favoring Cit+ evolution was a purpose or one of the purposes of the glucose-cycling (I also would like to know if there were other purposes of the glucose-cycling and exactly how any other purposes work). The fact that Cit+ evolution was observed once previously adds to my hunch that it was a goal. Also, the bacteria already had the ability to metabolize citrate and just needed to evolve a way to pass citrate through the cell wall.
::::Yes, I know it is there as a chelating agent -- but I also want to know if Cit+ evolution was a goal (again, a goal does not have to be an expected result and can even be an unlikely result) and if favoring Cit+ evolution was a purpose or one of the purposes of the glucose-cycling (I also would like to know if there were other purposes of the glucose-cycling and exactly how any other purposes work). The fact that Cit+ evolution was observed once previously adds to my hunch that it was a goal. Also, the bacteria already had the ability to metabolize citrate and just needed to evolve a way to pass citrate through the cell wall.