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.
| Strain | Phenotype | Color | araA alelle (codon) |
|---|---|---|---|
| REL606 | Ara– | 🔴 Red | 92D (GAC) |
| REL607 | Ara+ | ◯ White | 92G (GGC) |
| Other revertants | Ara+ | ◯ 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).
| Line | Agar Plate Growth Notes | Notes |
|---|---|---|
| Ara–1 🔴 | Normal | |
| Ara–2 🔴 | ≥20k some colonies fail to grow on MA, MG, and TA. Normal growth on LB. | Stable Polymorphism |
| Ara–3 🔴 | Normal | Citrate Utilization |
| Ara–4 🔴 | Normal | |
| Ara–5 🔴 | Normal | |
| Ara–6 🔴 | Normal | |
| Ara+1 ◯ | Normal | IS 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).