Fig. 3

The performance of the Drm-inactivated strains. a The engineering strategy proposed by GEM for de novo synthesis of purine nucleosides in B. subtilis. Genes/reactions in red indicate deletion and genes/reactions in green indicate overexpression. glcK, encoding glucokinase; zwf, encoding glucose-6-phosphate 1-dehydrogenase; ykgB, encoding 6-phosphogluconolactonase; pgi, encoding glucose-6-phosphate isomerase; ywjH, encoding transaldolase; tkt, encoding transketolase; prs, encoding ribose-phosphate pyrophosphokinase; purF, encoding amidophosphoribosyltransferase; drm, encoding pentose phosphate mutase; pgcA, encoding phosphoglucomutase; purR, Pur operon repressor. b The schematic diagram for the modifying strategies of drm inactivation. The engineered strains PN05, PN06, and PN07 were constructed by nonsense point mutation of the drm gene, deletion of the promoter P_drm, and knockout of the open reading frame, respectively. c The relative mRNA expression level of pupG gene in the engineering strains. The relative transcriptional levels were analyzed by quantitative real-time PCR using PN01 as the control. d The cell growth during shake-flask cultivation. The inset shows the growth curves in the seed medium. e The effect of the drm deficiency on the production of inosine and hypoxanthine. All error bars indicate ± SD, n = 3. A value of P less than 0.05 was regarded to be a significant difference with the control strain PN01 using the T-test (**, P < 0.01)