Abstract
BackgroundGenome sequencing revealed that Streptomyces sp. can dedicate up to ~ 10% of their genomes for the biosynthesis of bioactive secondary metabolites. However, the majority of these biosynthetic gene clusters are only weakly expressed or not at all. Indeed, the biosynthesis of natural products is highly regulated through integrating multiple nutritional and environmental signals perceived by pleiotropic and pathway-specific transcriptional regulators. Although pathway-specific refactoring has been a proved, productive approach for the activation of individual gene clusters, the construction of a global super host strain by targeting pleiotropic-specific genes for the expression of multiple diverse gene clusters is an attractive approach.ResultsStreptomyces albus J1074 is a gifted heterologous host. To further improve its secondary metabolite expression capability, we rationally engineered the host by targeting genes affecting NADPH availability, precursor flux, cell growth and biosynthetic gene transcriptional activation. These studies led to the activation of the native paulomycin pathway in engineered S. albus strains and importantly the upregulated expression of the heterologous actinorhodin gene cluster.ConclusionsRational engineering of Streptomyces albus J1074 yielded a series of mutants with improved capabilities for native and heterologous expression of secondary metabolite gene clusters.
Highlights
Genome sequencing revealed that Streptomyces sp. can dedicate up to ~ 10% of their genomes for the biosynthesis of bioactive secondary metabolites
Construction of S. albus engineered strains We used SCO5426 as the first gene probe encoding one of the three phosphofructokinases found in the S. coelicolor genome that is shown to upregulate actinorhodin through increased carbon flux into the pentose phosphate pathway [20]
The overexpression of crpSC gene had no effect on the growth rate of S. albus in R5A liquid media (Fig. 4b) but interfered with the sporulation process resulting in a white phenotype relative to wild type when S. albus grew on mannitolsoy flour agar (MS) solid media (Fig. 3b)
Summary
Genome sequencing revealed that Streptomyces sp. can dedicate up to ~ 10% of their genomes for the biosynthesis of bioactive secondary metabolites. Can dedicate up to ~ 10% of their genomes for the biosynthesis of bioactive secondary metabolites. Pathway-specific refactoring has been a proved, productive approach for the activation of individual gene clusters, the construction of a global super host strain by targeting pleiotropic-specific genes for the expression of multiple diverse gene clusters is an attractive approach. Talented bacteria, characterized by tens of secondary metabolite gene clusters, dedicate ~ 10% of their genomes to the corresponding biosynthetic functions [1]. The continuously reducing cost of genome sequencing renders the detection of diverse biosynthetic gene clusters rather a routine in a natural product research lab. Not much effort has been dedicated to the awakening of these metabolic pathways by modulating global regulators, which may have broader applicability for the heterologous expression of diverse biosynthetic gene clusters using S. albus as a host
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