The rph-pyrE Δ82-bp mutation. An 82-bp deletion in the rph-pyrE operon was found in 7 of 11 lactate adapted strains. The mutation maps to the end of the rph gene, just before the pyrE attenuator loop, causing the translational stop codon (TAG, shown in bold) to move from some distance upstream of the attenuator to just downstream of the loop, likely relieving repression of pyrE by the attenuator. The sequence in and around the deleted region of the operon is shown. The sequence of the deleted region is shown as highlighted, while a 10-bp sequence that repeats after 82 bp is surrounded with a box. The repeating sequence may explain the frequent occurrence of the deletion as a result of DNA polymerase slippage during DNA replication .