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Crib Sheet

This page collects some useful information related to studying the LTEE.

Arabinose Marker

REL606 and REL607 (the ancestral strains of the E. coli LTEE) 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 this codon to other amino acids are also known to confer an Ara+ phenotype.

StrainPhenotypeColoraraA alelle (codon)
REL606Ara–🔴 Red92D (GAC)
REL607Ara+◯ White92G (GGC)
Other revertantsAra+◯ White
92A (GCC)

Summary of Each Long-Term Line

After decades and tens of thousands of generations of evolution in the laboratory, E. coli cells in the different populations of the long-term experiment have diverged markedly in some of their characteristics. Some fail to grow on certain agar growth media. Many evolved elevated mutation rates (hypermutability).

LineAgar Plate Growth NotesNotes
Ara–1 🔴Normal
Ara–2 🔴≥20k some colonies fail to grow on MA, MG, and TA.
Normal growth on LB.
Stable Polymorphism
Ara–3 🔴NormalCitrate Utilization
Ara–4 🔴Normal
Ara–5 🔴Normal
Ara–6 🔴Normal
Ara+1 ◯NormalIS Element Mutator
Ara+2 ◯Normal
Ara+3 ◯Normal
Ara+4 ◯Normal
Ara+5 ◯Normal
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).