STUDIES ON THE PRODUCTION OF NUCLEOSIDES BY MICROORGANISMS

I. FORMATION OF RIBONUCLEOSIDES FROM BASES BY NUCLEOSIDE PRODUCING MUTANTS OF BACILLUS SUBTILIS

Abstract

(1) Inosine-producing mutants derived from Bacillus subtilis strains had a common characteristic of converting exogenously added hypoxanthine to inosine in high yields. Investigations on activities of the "salvage" synthesis and of degradation of inosine revealed that differences in the latter activities might mainly be related to differences of the former reaction.
(2) No. 11023, an inosine-producing mutant, degraded inosine to hypoxanthine 1/3-1/5 as much as the original strain. However, the strong activity of "salvage" synthesis seemed to completely suppress this degrading activity in inosine fermentation. Therefore, the "salvage" synthetic activity was thought essential for characterization as a typical inosine-producing mutant.
(3) On the "salvage" synthesis and de novo formation of inosine some interesting relationships were observed. Total amount of inosln ("salvage" synthesized plus de novo formed) was always far greater than that by de novo formation. De novo formation was much influenced by the culture medium, especially by ammonium and phosphate ion concentrations, but total inosine was nearly equal under these different conditions.
(4) "Salvage" syntheses of ribonucleosides from several kinds of bases by the original strain and many mutants were compared. Some interconversions of bases and nucleosides as well as "salvage" syntheses were observed. Both inosine- and xanthosine-producing mutants were capable of forming inosine and xanthosine from several kinds of purine bases, respectively.