High production of a class III lantipeptide AmfS in Streptomyces griseus

Heterologous Biosynthesis of New Lanthipeptides Nocardiopeptins with an Unprecedented Bridging Pattern of Lanthionine and Labionin

The class III lanthipeptide synthetase (LanKC) installs unusual amino acids, such as lanthionine and labionin, in lanthipeptides. Through genome mining, we discovered a new class III lanthipeptide synthetase coding gene (nptKC) and precursor peptide coding genes (nptA1, nptA2, and nptA3) in the genome of the actinobacterium Nocardiopsis alba. Coexpression experiments of the biosynthetic genes in Escherichia coli resulted in the production of new lanthipeptides named nocardiopeptins A1-A3. Analysis of two-dimensional NMR spectra after enzymatic degradation and partial basic hydrolysis of nocardiopeptin A2 revealed that labionin was located in lanthionine with opposite orientations, forming a nesting structure in nocardiopeptin A2. To the best of our knowledge, this bridging pattern in the lanthipeptides was unprecedented, indicating a novel reaction characteristic of the class III lanthipeptide synthetase NptKC.

Heterologous expression of lasso peptides with apparent participation in the morphological development in Streptomyces

Lasso peptides, ribosomally synthesized and post-translationally modified peptides, are primarily produced by bacteria and some archaea. Streptomyces lasso peptides have been known for their antimicrobial, anticancer, and antiviral properties. However, understanding their role in the morphology and production of secondary metabolites remains limited. We identified a previously unknown lasso peptide gene cluster in the genome of Streptomyces sp. L06. This gene cluster (LASS) produces two distinct lasso peptides, morphosin-1 and - 2. Notably, morphosin-2 is a member of a new subfamily of lasso peptides, with BGCs exhibiting a similar structure. When LASS was expressed in different Streptomyces hosts, it led to exciting phenotypic changes, including the absence of spores and damage in aerial mycelium development. In one of the hosts, LASS even triggered antibiotic formation. These findings open up a world of possibilities, suggesting the potential role of morphosins in shaping Streptomyces' morphological and biochemical development.

Heterologous production of a new lanthipeptide boletupeptin using a cryptic biosynthetic gene cluster of the myxobacterium Melittangium boletus

Myxobacteria have comparatively large genomes that contain many biosynthetic genes with the potential to produce secondary metabolites. Based on genome mining, we discovered a new biosynthetic gene cluster of class III lanthipeptide in the genome of the myxobacterium Melittangium boletus. The biosynthetic gene cluster contained a precursor peptide-coding gene bolA, and a class III lanthipeptide synthetase-coding gene bolKC. The expression vector containing bolA and bolKC was constructed using synthetic DNA with codon-optimized sequences based on the commercially available vector pET29b. Co-expression of the two genes in the host Escherichia coli BL21(DE3) yielded a new class III lanthipeptide named boletupeptin. The structure of boletupeptin was proposed to have one unit of labionin, as determined by mass spectrometry experiments after reductive cleavage. This is the first report of a class III lanthipeptide from a myxobacterial origin.

Heterologous Production and Structure Determination of a New Lanthipeptide Sinosporapeptin Using a Cryptic Gene Cluster in an Actinobacterium Sinosporangium siamense

Lipolanthine is a subclass of lanthipeptide that has the modification of lipid moiety at the N-terminus. A cryptic biosynthetic gene cluster comprising four genes (sinA, sinKC, sinD, and sinE) involved in the biosynthesis of lipolanthine was identified in the genome of an actinobacterium Sinosporangium siamense. Heterologous coexpression of a precursor peptide coding gene sinA and lanthipeptide synthetase coding gene sinKC in the host Escherichia coli strain BL21(DE3) resulted in the synthesis of a new lanthipeptide, sinosporapeptin. It contained unusual amino acids, including one labionin and two dehydrobutyrine residues, as determined using NMR and MS analyses. Another coexpression experiment with two additional genes of decarboxylase (sinD) and N-acetyl transferase (sinE) resulted in the production of a lipolanthine-like modified sinosporapeptin.

Refactoring and Heterologous Expression of Class III Lanthipeptide Biosynthetic Gene Clusters Lead to the Discovery of N,N-Dimethylated Lantibiotics from Firmicutes

Class III lanthipeptides are an emerging subclass of lanthipeptides, representing an underexplored trove of new natural products with potentially broad chemical diversity and important biological activity. Bioinformatic analysis of class III lanthipeptide biosynthetic gene cluster (BGC) distribution has revealed their high abundance in the phylum Firmicutes. Many of these clusters also feature methyltransferase (MT) genes, which likely encode uncommon class III lanthipeptides. However, two hurdles, silent BGCs and low-yielding pathways, have hindered the discovery of class III lanthipeptides from Firmicutes. Here, we report the design and construction of a biosynthetic pathway refactoring and heterologous overexpression strategy which seeks to overcome these hurdles, simultaneously activating and increasing the production of these Firmicutes class III lanthipeptides. Applying our strategy to MT-containing BGCs, we report the discovery of new class III lanthipeptides from Firmicutes bearing rare N,N-dimethylations. We reveal the importance of the first two amino acids in the N-terminus of the core peptide in controlling the MT dimethylation activity. Leveraging this feature, we engineer class III lanthipeptides to enable N,N-dimethylation, resulting in significantly increased antibacterial activity. Furthermore, the refactoring and heterologous overexpression strategy showcased in this study is potentially applicable to other ribosomally synthesized and post-translationally modified peptide BGCs from Firmicutes, unlocking the genetic potential of Firmicutes for producing peptide natural products.

Mechanism of Action of Ribosomally Synthesized and Post-Translationally Modified Peptides

Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a natural product class that has undergone significant expansion due to the rapid growth in genome sequencing data and recognition that they are made by biosynthetic pathways that share many characteristic features. Their mode of actions cover a wide range of biological processes and include binding to membranes, receptors, enzymes, lipids, RNA, and metals as well as use as cofactors and signaling molecules. This review covers the currently known modes of action (MOA) of RiPPs. In turn, the mechanisms by which these molecules interact with their natural targets provide a rich set of molecular paradigms that can be used for the design or evolution of new or improved activities given the relative ease of engineering RiPPs. In this review, coverage is limited to RiPPs originating from bacteria.

A Multidisciplinary Approach to Unraveling the Natural Product Biosynthetic Potential of a Streptomyces Strain Collection Isolated from Leaf-Cutting Ants

The rapid emergence of bacterial resistance to antibiotics has urged the need to find novel bioactive compounds against resistant microorganisms. For that purpose, different strategies are being followed, one of them being exploring secondary metabolite production in microorganisms from uncommon sources. In this work, we have analyzed the genome of 12 Streptomyces sp. strains of the CS collection isolated from the surface of leaf-cutting ants of the Attini tribe and compared them to four Streptomyces model species and Pseudonocardia sp. Ae150A_Ps1, which shares the ecological niche with those of the CS collection. We used a combination of phylogenetics, bioinformatics and dereplication analysis to study the biosynthetic potential of our strains. 51.5% of the biosynthetic gene clusters (BGCs) predicted by antiSMASH were unknown and over half of them were strain-specific, making this strain collection an interesting source of putative novel compounds.

De novo biosynthesis of garbanzol and fustin in Streptomyces albus based on a potential flavanone 3-hydroxylase with 2-hydroxylase side activity

Flavonoids are important plant secondary metabolites, which were shown to have antioxidant, anti-inflammatory or antiviral activities. Heterologous production of flavonoids in engineered microbial cell factories is an interesting alternative to their purification from plant material representing the natural source. The use of engineered bacteria allows to produce specific compounds, independent of soil, climatic or other plant-associated production parameters. The initial objective of this study was to achieve an engineered production of two interesting flavanonols, garbanzol and fustin, using Streptomyces albus as the production host. Unexpectedly, the engineered strain produced several flavones and flavonols in the absence of the additional expression of a flavone synthase (FNS) or flavonol synthase (FLS) gene. It turned out that the heterologous flavanone 3-hydroxylase (F3H) has a 2-hydroxylase side activity, which explains the observed production of 7,4'-dihydroxyflavone, resokaempferol, kaempferol and apigenin, as well as the biosynthesis of the extremely rare 2-hydroxylated intermediates 2-hydroxyliquiritigenin, 2-hydroxynaringenin and probably licodione. Other related metabolites, such as quercetin, dihydroquercetin and eriodictyol, have also been detected in culture extracts of this recombinant strain. Hence, the enzymatic versatility of S. albus can be conveniently exploited for the heterologous production of a large diversity of plant metabolites of the flavonoid family.