Thymidine sensitivity of certain strains of Escherichia coli K12

In studies on thymineless death in Escherichia coli K12, it was noted that certain thymine requiring mutants were inhibited by thymidine. The pattern of inhibition varied with the conditions and media employed. Accumulation of deoxyribose-5-phosphate as a possible reason for inhibition is ruled out since the strains are deoB- (formerly drm-) and synthesize deoxyriboaldolase constitutively. We report this inhibition to alert investigators who study thymidine metabolism or use thymidine to label the DNA.