Involvement of synthesis of RNA in thymineless death

Abstract

THE phenomenon of thymineless death in bacteria1 is of particular interest because of its apparent relationship to DNA replication, as shown by Maaløe and Hanawalt2. Only those bacterial cells which are synthesizing DNA at the time thymine is removed from the culture medium appear to be susceptible to thymineless killing under conditions of protein synthesis inhibition3. The 97 per cent susceptible fraction from an exponentially growing culture of strain TAU (E. coli 15T-A-U-, requiring thymine, arginine and uracil) succumbs to the lethality of thymine deficiency at about the same rate whether arginine and uracil are present or not2. Thus, little correlation exists between thymineless killing and cytoplasmic synthesis. Using E. coli B3 Gallant and Suskind4 also reported thymineless death under conditions of protein synthesis inhibition, but they found further that phosphate starvation prevented killing. They implicated RNA synthesis on the basis of this result and the finding that the inhibitory effect of 5-methyl tryptophan could be partially reversed (with respect to RNA synthesis and thymineless killing) by chloramphenicol. The investigations to be reported here provide evidence that messenger-RNA synthesis in particular is necessary for the killing event in thymine-deficient cultures. © 1963 Nature Publishing Group.