Feedback Inhibition of Purine Biosynthesis in Adenine-Excreting Mutant of Salmonella typhimurium.

Abstract

Two phenotypic types of mutants resistant to 2, 6-diaminopurine (DAP) were isolated from S. typhimurium. The mutants differed in cross-resistance patterns with other purine analogs. One type (dap-r-3) differed from the other (dap-r-6) in its ability to allow satellite growth of the parent sensitive strain plated in inhibitory concentrations of DAP and adenine. This phenomenon was explained by the abnormal excretion of adenine and uracil which could prevent inhibition of sensitive strain by DAP and adenine respectively. Excretions of these compounds were not directly responsible for resistance to DAP since similar mutations were demonstrated in auxotrophic mutants deficient in de novo synthesis of adenine or uracil.