Investigation of the effects of actinorhodin biosynthetic gene cluster expression and a rpoB point mutation on the metabolome of Streptomyces coelicolor M1146.

The previously reported Streptomyces coelicolor M1146 is commonly used as a host strain for engineering of secondary metabolite production. In this study, absolute quantification of intracellular and extracellular metabolites of M1146 was performed in mid-log phase and stationary phase to observe major metabolites and the changes that occurred during growth. Decreased levels of central carbon metabolites (glycolysis, TCA cycle, and pentose phosphate pathway) and increased levels of amino acids were observed in stationary phase compared to mid-log phase. Furthermore, comparative metabolome analyses of M1146 upon expression of the actinorhodin biosynthetic gene cluster (M1146+ACT), a point mutation on the rpoB gene encoding RNA polymerase beta-subunit (M1152), and both expression of actinorhodin biosynthetic gene cluster and a rpoB point mutation (M1152+ACT) were performed. M1146+ACT showed higher levels of important cofactors, such as ATP, NADPH, and FMN while M1152 led to higher levels of intracellular S-adenosyl-methionine, acyl-CoAs, and extracellular nucleosides compared to M1146. M1152+ACT exhibited the highest levels of actinorhodin with elevated bases, nucleosides, and nucleotides, such as intracellular PRPP (phosphoribosyl phosphate), ATP, along with extracellular inosine, uridine, and guanine compared to the other three strains, which were considered to be combined effects of actinorhodin gene cluster expression and a rpoB point mutation. Metabolites analysis by means of absolute quantification demonstrated changes in precursors of secondary metabolites before and after phosphate depletion in M1146. Comparative metabolome analysis provided further insights into the effects of actinorhodin gene cluster expression along with a rpoB point mutation on the metabolome of S. coelicolor.

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