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Talk:Flaws in Richard Lenski Study (view source)
Revision as of 23:55, July 15, 2008
, 23:55, July 15, 2008→Richard Lenski incorrectly included generations of the E. coli already known to contain Cit+ variants in his experiments.[3] Once these generations are removed from the analysis, the data disprove Len
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:::::Actually the methods cited in the paper would separate the Cit+ lines from the Cit-. They took single colonies (founded by single cells), and tested them on selective agar (minimal citrate media - MC agar) and an indicator medium, Christensen's citrate agar (Product information from Sigma here: http://www.sigmaaldrich.com/sigma/datasheet/c7595dat.pdf). As Gerlach notes from the Blount paper, Christensen's citrate agar is very sensitive to citrate utilization. E.coli strains do not produce a color change but other citrate-using enterics like ''S. typhimurium'' and Cit+ ''E. coli'' mutants appear pink/red on the plates.
:::::Actually the methods cited in the paper would separate the Cit+ lines from the Cit-. They took single colonies (founded by single cells), and tested them on selective agar (minimal citrate media - MC agar) and an indicator medium, Christensen's citrate agar (Product information from Sigma here: http://www.sigmaaldrich.com/sigma/datasheet/c7595dat.pdf). As Gerlach notes from the Blount paper, Christensen's citrate agar is very sensitive to citrate utilization. Typical ''E. coli'' strains do not produce a color change but other citrate-using enterics like ''S. typhimurium'' and Cit+ ''E. coli'' mutants appear pink/red on the plates.
:::::This conclusion is further validated (as I mention above), by the fact that Cit+ mutants did not appear immediately in the replay experiments (Others have also noted this). For example, in replay set-1, it took 750 generations before the first Cit+ mutants were isolated. Many didn't produce Cit+ cells after 3700 generations. If the starting line was Cit+, *all* the cells in the culture would have show up as Cit+ in the first pass.
:::::This conclusion is further validated (as I mention above), by the fact that Cit+ mutants did not appear immediately in the replay experiments (Others have also noted this). For example, in replay set-1, it took 750 generations before the first Cit+ mutants were isolated. Many didn't produce Cit+ cells after 3700 generations. If the starting line was Cit+, *all* the cells in the culture would have show up as Cit+ in the first pass.