Genome shuffling of Streptomyces viridochromogenes for improved production of avilamycin

Avilamycin is one of EU-approved antimicrobial agents in feed industry to inhibit the growth of multidrug-resistant Gram-positive bacteria. Here, we applied a process of combining ribosome engineering and genome shuffling to achieve rapid improvement of avilamycin production in Streptomyces viridochromogenes AS 4.126. The starting mutant population was generated by Co-60 gamma-irradiation treatments of the spores. After five rounds of protoplast fusion with streptomycin-resistance screening, an improved recombinant E-219 was obtained and its yield of avilamycin reached 1.4 g/L, which was increased by 4.85-fold and 36.8-fold in comparison with that of the shuffling starter Co gamma-316 and the ancestor AS 4.126. Furthermore, the mechanism for the improvement of shuffled strains was investigated. Recombinants with enhanced streptomycin resistance exhibited significantly higher avilamycin production and product resistance, probably due to the mutations in the ribosome protein S12. The morphological difference between the parent mutant and shuffled recombinant was observed in conidiospore, and hyphae pellets. The presence of genetic diversity among shuffled populations with varied avilamycin productivity was confirmed by randomly amplified polymorphic DNA analysis. In summary, our results demonstrated that genome shuffling combined with ribosome engineering was a powerful approach for molecular breeding of high-yield industrial strains.