Development of sp. FR-008 as an emerging chassis.

Microbial-derived natural products are important in both the pharmaceutical industry and academic research. As the metabolic potential of original producer especially is often limited by slow growth rate, complicated cultivation profile, and unfeasible genetic manipulation, so exploring a as a super industrial chassis is valuable and urgent. sp. FR-008 is a fast-growing microorganism and can also produce a considerable amount of macrolide candicidin via modular polyketide synthase. In this study, we evaluated sp. FR-008 as a potential industrial-production chassis. First, PacBio sequencing and transcriptome analyses indicated that the sp. FR-008 genome size is 7.26 Mb, which represents one of the smallest of currently sequenced genomes. In addition, we simplified the conjugation procedure without heat-shock and pre-germination treatments but with high conjugation efficiency, suggesting it is inherently capable of accepting heterologous DNA. In addition, a series of promoters selected from literatures was assessed based on GusA activity in sp. FR-008. Compared with the common used promoter -p, the strength of these promoters comprise a library with a constitutive range of 60-860%, thus providing the useful regulatory elements for future genetic engineering purpose. In order to minimum the genome, we also target deleted three endogenous polyketide synthase (PKS) gene clusters to generate a mutant LQ3. LQ3 is thus an "updated" version of sp. FR-008, producing fewer secondary metabolites profiles than sp. FR-008. We believe this work could facilitate further development of sp. FR-008 for use in biotechnological applications.