TABLE 1

Growth of stationary-phase revertants on alternative selection mediad

Strain and selection mediumNo. of revertants that showed the following phenotype/no. of revertants analyzed (%)
His+ Met+ Leu+His+ Met+Met+ Leu+His+ Leu+Single revertant (His+, Met+, or Leu+)
ΔytcG strain
    His27/100 (27)2/100 (2)71/100 (71)a
    Met7/100 (7)4/100 (4)89/100 (89)b
    Leu22/100 (22)7/100 (7)2/100 (2)69/100 (69)c
YB955
    His3/100 (3)10/100 (10)87/100 (77)a
    Met2/100 (2)47/100 (47)51/100 (51)b
    Leu100/100 (100)c
Pspac-nrdEF strain (with nrdEF inactivated)
    His3/54 (5)51/54 (95)a
    Met5/19 (26)14/19 (74)b
    Leu50/50
  • a His+ revertants.

  • b Met+ revertants.

  • c Leu+ revertants.

  • d His+, Met+, and Leu+ revertants from day 4, 6, or 8 were screened on 1× SMM missing one required amino acid (His, Met, or Leu [His, Met, or Leu, respectively) to screen for suppressor mutations. Plates were scored after 48 h of incubation.