Engineering Salinispora tropica for heterologous expression of natural product biosynthetic gene clusters
The marine actinomycete genus Salinispora is a remarkably prolific source of structurally diverse and biologically active secondary metabolites. Herein, we select the model organism Salinispora tropica CNB-440 for development as a heterologous host for the expression of biosynthetic gene clusters (BGCs) to complement well-established Streptomyces host strains. In order to create an integratable host with a clean background of secondary metabolism, we replaced three genes (salA–C) essential for salinosporamide biosynthesis with a cassette containing the Streptomyces coelicolor ΦC31 phage attachment site attB to generate the mutant S. tropica CNB-4401 via double-crossover recombination. This mutagenesis not only knocks-in the attachment site attB in the genome of S. tropica CNB-440 but also abolishes production of the salinosporamides, thereby simplifying the strain’s chemical background. We validated this new heterologous host with the successful integration and expression of the thiolactomycin BGC that we recently identified in several S. pacifica strains. When compared to the extensively engineered superhost S. coelicolor M1152, the production of thiolactomycins from S. tropica CNB-4401 was approximately 3-fold higher. To the best of our knowledge, this is the first example of using a marine actinomycete as a heterologous host for natural product BGC expression. The established heterologous host may provide a useful platform to accelerate the discovery of novel natural products and engineer biosynthetic pathways.
KeywordsHeterologous expression Salinispora Natural products Genetic engineering
We kindly thank W. Fenical and P. R. Jensen (Scripps Institution of Oceanography, UCSD) for providing the S. tropica strain, and P. R. Jensen and N. Ziemert (Scripps Institution of Oceanography, UCSD) for valuable discussion.
X.T. and B.S.M. designed the research. X.T., J.J.Z., and B.S.M. performed the experiments and analyzed the data. X.T., J.J.Z., and B.S.M. wrote the manuscript.
This study was supported by a graduate fellowship from the National Science Foundation to J.J.Z. and National Institutes of Health grants F31-AI129299 to J.J.Z. and R01-GM085770 and R01-AI117712 to B.S.M.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
This article does not contain any studies with human participants or animals performed by any of the authors.
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