---++ Selecting Arabinose Marker Revertants ---+++ Background The _Escherichia coli B_ strain REL606 has a mutation in the _araA_ gene that renders it unable to utilize the sugar L-arabinose. Strain REL607 is a spontaneous revertant of REL606 containing a single point mutation that restores the ability to metabolize L-arabinose. This marker is selectively neutral in a variety of conditions and can be used to determine the relative frequencies of Ara- (REL606-derived) and Ara+ (REL607-derived) cells in a mixture for competition assays or marker divergence experiments. Ara- and Ara+ cells form red and white colonies, respectively, on tetrazolium arabinose (TA) plates, because utilization of the sugar rather than only the tryptone and yeast extract components of this medium causes the excretion of acetic acid which acidifies the area surrounding the colony, changing the tetrazolium indicator color from red to white. | *strain* | *marker* | *<i>araA</i> sequence* | | REL606 | Ara- | 92D (GAC) | | REL607 | Ara+ | 92G (GGC) | Selections for arabinose utilization from REL606 is known to also produce Ara+ revertants that have an _araA_ 92A (GCC) sequence. ---+++ Selection of Ara+ Revertants from Ara- Strains Derived from REL606 ---+++ RFLP Assay for Verifying the REL607 Mutation *Primers* | REL256 | REL606/70660-70683 | 5'-CCGATACGCTCATGGGCTTGTTTA | | REL257 | REL606/71177-71154 | 5'-CTGCCCAGGCCGTTGCGACTCTAT | | *Strain* | *Marker* | *RFLP Fragment Sizes* | | REL606 | Ara- | 226, 197, 72 (bp) | | REL607 | Ara+ | 207, 197, 72, 19 (bp) |
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Topic revision: r2 - 2008-05-29 - JeffreyBarrick