Engineering the Erythromycin-Producing Strain HOE107 for the Heterologous Production of Polyketide Antibiotics.

Bacteria of the genus produce important polyketide antibiotics, including erythromycin A () and spinosad (). We herein report the development of an industrial erythromycin-producing strain, . HOE107, into a host for the heterologous expression of polyketide biosynthetic gene clusters (BGCs) from other species and related actinomycetes. To facilitate the integration of natural product BGCs and auxiliary genes beneficial for the production of natural products, the erythromycin polyketide synthase () genes were replaced with two bacterial genomic integration sites associated with bacteriophages ϕC31 and ϕBT1. We also established a highly efficient conjugation protocol for the introduction of large bacterial artificial chromosome (BAC) clones into strains. Based on this optimized protocol, an arrayed BAC library was effectively transferred into . The large spinosad gene cluster from and the actinorhodin gene cluster from were successfully expressed in the deletion mutant. Deletion of the endogenous giant polyketide synthase genes -, the product of which is not known, and the flaviolin gene cluster () from the bacterium increased the heterologous production of spinosad and actinorhodin. Furthermore, integration of pJTU6728 carrying additional beneficial genes dramatically improved the yield of actinorhodin in the engineered strains. Our study demonstrated that the engineered strains SLQ185, LJ161, and LJ162 are good hosts for the expression of heterologous antibiotics and should aid in expression-based genome-mining approaches for the discovery of new and cryptic antibiotics from and rare actinomycetes.