Overexpression of SRO_3163, a homolog of Streptomyces antibiotic regulatory protein, induces the production of novel cyclohexene-containing enamide in Streptomyces rochei

Exploring the Synthetic Potential of Horner-Wadsworth-Emmons Reaction Toward the Synthesis of Polyketide Based Natural Products: A Review

The Horner-Wadsworth-Emmons (HWE) reaction is a commonly used and reliable phenomenon for carbon-carbon olefination in organic chemistry, carried out by treating aldehyde or ketones with phosphonate esters to afford the substituted alkenes. HWE reaction has also been observed to be involved in the stereo-controlled syntheses of naturally occurring compounds that acquire pharmaceutical profiles against various diseases. In this article, recent implementations of Horner-Wadsworth-Emmons reaction towards the notable total syntheses of naturally occurring compounds such as polyketides have been summarized.

Expression of Syo_1.56 SARP Regulator Unveils Potent Elasnin Derivatives with Antibacterial Activity

Actinomycetes are prolific producers of natural products, particularly antibiotics. However, a significant proportion of its biosynthetic gene clusters (BGCs) remain silent under typical laboratory conditions. This limits the effectiveness of conventional isolation methods for the discovery of novel natural products. Genetic interventions targeting the activation of silent gene clusters are necessary to address this challenge. Streptomyces antibiotic regulatory proteins (SARPs) act as cluster-specific activators and can be used to target silent BGCs for the discovery of new antibiotics. In this study, the expression of a previously uncharacterized SARP protein, Syo_1.56, in Streptomyces sp. RK18-A0406 significantly enhanced the production of known antimycins and led to the discovery of 12 elasnins (1-12), 10 of which were novel. The absolute stereochemistry of elasnin A1 was assigned for the first time to be 6S. Unexpectedly, Syo_1.56 seems to function as a pleiotropic rather than cluster-specific SARP regulator, with the capability of co-regulating two distinct biosynthetic pathways, simultaneously. All isolated elasnins were active against wild-type and methicillin-resistant Staphylococcus aureus with IC50 values of 0.5-20 μg/mL, some of which (elasnins A1, B2, and C1 and proelasnins A1, and C1) demonstrated moderate to strong antimalarial activities against Plasmodium falciparum 3D7. Elasnins A1, B3, and C1 also showed in vitro inhibition of the metallo-β-lactamase responsible for the development of highly antibiotic-resistant bacterial strains.

Promoter engineering of natural product biosynthetic gene clusters in actinomycetes: concepts and applications

Covering 2011 to 2022Low titers of natural products in laboratory culture or fermentation conditions have been one of the challenging issues in natural products research. Many natural product biosynthetic gene clusters (BGCs) are also transcriptionally silent in laboratory culture conditions, making it challenging to characterize the structures and activities of their metabolites. Promoter engineering offers a potential solution to this problem by providing tools for transcriptional activation or optimization of biosynthetic genes. In this review, we summarize the 10 years of progress in promoter engineering approaches in natural products research focusing on the most metabolically talented group of bacteria actinomycetes.

Transcriptional regulators of secondary metabolite biosynthesis in Streptomyces

In the post-genome era, great progress has been made in metabolic engineering using recombinant DNA technology to enhance the production of high-value products by Streptomyces. With the development of microbial genome sequencing techniques and bioinformatic tools, a growing number of secondary metabolite (SM) biosynthetic gene clusters in Streptomyces and their biosynthetic logics have been uncovered and elucidated. In order to increase our knowledge about transcriptional regulators in SM of Streptomyces, this review firstly makes a comprehensive summary of the characterized factors involved in enhancing SM production and awakening SM biosynthesis. Future perspectives on transcriptional regulator engineering for new SM biosynthesis by Streptomyces are also provided.

Isolation of Hydrazide-alkenes with Different Amino Acid Origins from an Azoxy-alkene-Producing Mutant of Streptomyces rochei 7434AN4

A triple mutant (strain KA57) of Streptomyces rochei 7434AN4 produces an azoxy-alkene compound, KA57A, which was not detected in a parent strain or other single and double mutants. This strain accumulated several additional minor components, whose structures were elucidated. HPLC analysis of strain KA57 indicated the presence of two UV active components (KA57D1 and KA57D2) as minor components. They exhibited a maximum UV absorbance at 218 nm, whereas a UV absorbance of azoxy-alkene KA57A was detected at 236 nm, suggesting that both KA57D1 and KA57D2 contain a different chromophore from KA57A. KA57D1 has a molecular formula of C12H22N2O2, and NMR analysis revealed KA57D1 is a novel hydrazide-alkene compound, (Z)-N-acetyl-N'-(hex-1-en-1-yl)isobutylhydrazide. Labeling studies indicated that nitrogen Nβ of KA57D1 is derived from l-glutamic acid, and the isobutylamide unit (C-1 to C-3, 2-Me, and Nα) originates from valine. KA57D2 has a molecular formula of C13H24N2O2, and its structure was determined to be (Z)-N-acetyl-N'-(hex-1-en-1-yl)-2-methylbutanehydrazide, in which a 2-methylbutanamide unit was shown to originate from isoleucine. Different biogenesis of the Nα atom (l-serine for KA57A, l-valine for KA57D1, and l-isoleucine for KA57D2) indicates the relaxed substrate recognition for nitrogen-nitrogen bond formation in the biosyntheses of KA57A, KA57D1, and KA57D2.

Characterization of the surugamide biosynthetic gene cluster of TUA-NKU25, a Streptomyces diastaticus strain isolated from Kusaya, and its effects on salt-dependent growth

Kusaya, a traditional Japanese fermented fish product, is known for its high preservability, as it contains natural antibiotics derived from microorganisms, and therefore molds and yeasts do not colonize it easily. In this study, the Streptomyces diastaticus strain TUA-NKU25 was isolated from Kusaya, and its growth as well as the production of antibiotics were investigated. Strain TUA-NKU25 showed advantageous growth characteristics in the presence, but not in the absence, of sodium chloride (NaCl). Antimicrobial assay, high-performance liquid chromatography, and electrospray ionization-mass spectrometry analysis showed that this strain produced surugamide A and uncharacterized antimicrobial compound(s) during growth in the presence of NaCl, suggesting that the biosynthesis of these compounds was upregulated by NaCl. Draft genomic analysis revealed that strain TUA-NKU25 possesses a surugamide biosynthetic gene cluster (sur BGC), although it is incomplete, lacking surB/surC. Phylogenetic analysis of strain TUA-NKU25 and surugamide-producing Streptomyces showed that sur BGC formed a clade distinct from other known groups.