Biological investigations of 6-azathymine, a thymine analog.

Summary 6-Azathymine (3,5-dihydroxy-6-methyl-1,2,4-triazine) competitively inhibited the growth of S. faecalis and L. casei in media supplemented with thymine or thymidine. A significantly greater amount of the analog was required for 50 per cent inhibition of growth in the presence of thymidine than with thymine. In media supplemented with pteroylglutamic acid or synthetic citrovorum factor, 6-azathymine noncompetitively inhibited the growth of S. faecalis . Although azathymine was essentially noninhibitory for Leuconostoc citrovorum growing on a medium containing either thymidine or synthetic citrovorum factor, it completely inhibited the growth of L. leichmannii , not only on thymidine but also on vitamin B 12 and pteroylglutamic acid in the absence of exogenous thymidine. The significance of these results for the pathways of thymine and thymidine utilization has been discussed. The compound had no apparent effect on the development of the chick embryo.