TABLE 2

Base changes in revertants of mutant allelese

Phenotype and revertant allelePosition(s) of mutation (bp)No. of revertants with mutation/no. of revertants sequencedType of mutationDNA changeResult of mutation
His+ Met+ Leu+a
    hisC95222/30TransitionT → CStop → Gln
    hisCNF8/30NFNFNF
    metB34619/30TransversionT → GStop → Glu
    metB346 and 3482/30TransversionT → G and A → TStop → Asp
    metBNF9/30NFNFNF
    leuC42719/30TransitionA → GArg → Gly
    leuCNF11/30NFNFNF
Met+b
    metB3466/10TransitionT → CStop → Gln
    metB3462/10TransitionT → AStop → Lys
    metBNF2/10NFNFNF
His+c
    hisC9524/10TransitionT → CStop → Gln
    hisC9522/10TransversionT → GStop → Glu
    hisC9534/10TransitionA → GStop → Trp
Leu+,d leuCNF10/10NFNFNF
  • a Revertants were selected in histidine dropout medium (7/30 revertants) or methionine dropout medium (23/30 revertants).

  • b Revertants were selected in methionine dropout medium (10 revertants).

  • c Revertants were selected in histidine dropout medium (10 revertants).

  • d Revertants were selected in leucine dropout medium (10 revertants).

  • e Revertants were tested for their ability to grow on 1× SMM lacking histidine, methionine, and leucine and classified for their phenotype. Fragments of the hisC, metB, and leuC genes were sequenced depending on the observed reversion. NF, no changes were found in the sequenced fragment.