Fig. 1
Traditional engineering of Bacillus subtilis for de novo synthesis of purine nucleosides. a Biosynthetic pathway of purine nucleosides in B. subtilis. prs, encoding PRPP synthetase; purEKBCSQLFMNHD (pur operon), encoding enzymes required to synthesize IMP from PRPP; Ppur, purine operon promoter; purA, encoding adenylosuccinate synthase; purB, encoding adenylosuccinate lyase; guaB, encoding IMP dehydrogenase; guaA, encoding GMP synthetase; guaC, encoding GMP reductase; deoD, encoding purine nucleoside phosphorylase (PNP); pupG, encoding PNP; apt, encoding adenine phosphoribosyltransferase; hpt, encoding hypoxanthine–guanine phosphoribosyltransferase; xpt, encoding xanthine phosphoribosyltransferase; Ado, adenosine; Ino, inosine; Xao, xanthosine; Guo, guanosine; Ade, adenine; Hyp, hypoxanthine; Xan, xanthine; Gua, guanine. b Construction of engineered strains for de novo synthesis of inosine by traditional metabolic engineering. c The growth curve in seed cultivation. d Growth curve by shake-flask cultivation. Data shown are mean values from three biological replicates and a value of P less than 0.05 is regarded to be a significant difference with that of W168 strain using the T-test (**, P < 0.01)