Rational construction of rpsL or/and rpoB merodiploids affects biosynthesis of secondary metabolite in Streptomyces

Ribosome engineering technology typically involves resistance screening of streptomycin and rifampin to introduce point mutations in genes ribosomal protein S12 (rpsL) or RNA polymerase (rpoB), thereby enhancing the synthesis level of secondary metabolites in Streptomyces. Currently, directly introducing copies of genes rpsL and rpoB carrying "beneficial mutations" to construct diploids has become a more rapid and efficient method for obtaining high-yielding Streptomyces strains.

We directly introduced these beneficial mutations (rpsL: K88E/P91S; rpoB: S433L/H437Y/R440C) to construct single or combined merodiploids. Introducing rpsL-K88E promoted secondary metabolite biosynthesis in both strains S. coelicolor M145 and S. diastatochromogenes 1628, notably increasing tetramycin A production by 66% in 1628-rpsL-K88E. However, rpsL-P91S yielded no significant positive effects. Regarding rpoB, the M145-rpoB-H437Y strain showed a modest enhancement, with actinorhodin and undecylprodigiosin yields increasing by 20% and 22%. In S. diastatochromogenes 1628, introducing rpoB-H437Y, rpoB-R440C and rpoB-S433L promoted the synthesis of toyocamycin and tetraene macrolides to varying degrees.

Constructing a diploid by directly introducing the rpsL and rpoB genes carrying "beneficial mutations" is an effective strategy to enhance the synthesis level of secondary metabolites, whether for the model strain S. coelicolor M145 or the industrial strain S. diastatochromogenes 1628.