The Lenski Long-Term Evolution Experiment

Arabinose Marker

REL606 and REL607 (the ancestral strains of the E. coli long-term evolution experiment) differ by a single point mutation in the araA gene. This mutation was originally present in REL606. It makes an excellent neutral marker for evolution and competition experiments. REL607 was selected as a spontaneous arabinose-utilizing revertant from REL607. Most spontaneous revertants selected from a strain with the REL606 araA allele have the REL607 allele, but other mutations at this amino acid are also known to confer an Ara+ phenotype.

Strain Phenotype Color araA allele
REL606 Ara- led-box-red Red 92D (GAC)
REL607 Ara+ led-box-gray White 92G (GGC)
other revertants Ara+ led-box-gray White 92A (GCC)

Color of colonies when grown on tetrazolium arabinose (TA) plates.

Summary of the Known Idiosyncrasies of Each Long-Term Line

After more than 20 years and 40,000 generations of evolution in the laboratory, the various experimental replicates of the long-term experiment have diverged markedly. Some fail to grow on certain media.

Line Growth Other Notes
led-box-red Ara-1 Normal  
led-box-red Ara-2 ≥20k some colonies fail to grow on MA, MG, and TA.
Normal growth on LB.
Stable Polymorphism
led-box-red Ara-3 Normal  
led-box-red Ara-4 Normal  
led-box-red Ara-5 Normal  
led-box-red Ara-6 Normal  
led-box-gray Ara+1 Normal  
led-box-gray Ara+2 Normal  
led-box-gray Ara+3 Normal  
led-box-gray Ara+4 Normal  
led-box-gray Ara+5 Normal  
led-box-gray Ara+6 ≥10k unreliable growth on TA and LB, no growth on MA.
Normal growth on MG.

Key to Media: minimal arabinose (MA), minimal glucose (MG), tetrazolium arabinose (TA).

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Topic revision: r3 - 18 May 2010 - 02:41:31 - Main.JeffreyBarrick
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