Purine metabolism in Neisseria gonorrhoeae: the requirement for hypoxanthine

Abstract

Strains isolated from disseminated gonococcal infections often require hypoxanthine for growth. The biochemical bases for the requirement for hypoxanthine in strains isolated from both disseminated (Ile⁻Val⁻Arg⁻Hyx⁻Ura⁻phenotype) and non-disseminated (Hyx⁻phenotype) infections were compared. The requirement for hypoxanthine was dependent upon the composition of the growth medium. In a complete defined medium, hypoxanthine was replaced by a mixture of adenine and guanine but not by either purine alone. The addition of adenine alone inhibited gonococcal growth. This inhibition was reversed by the addition of guanine and most likely resulted from an inhibition of de novo purine biosynthesis. In a histidine-free medium, adenine replaced the hypoxanthine requirement in Ile⁻Val⁻Arg⁻Hyx⁻Ura⁻ strains. Adenine did not replace the hypoxanthine requirement in Hyx⁻ strains. The Ile⁻Val⁻Arg⁻Hyx⁻Ura⁻ strains exhibited a markedly reduced rate of de novo purine biosynthesis while Hyx⁻ strains were blocked in this pathway. In vivo concentrations of purines are important factors which may limit the intracellular or extracellular growth of these strains.