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Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pyrrolizidine alkaloids (PAs) are a structurally diverse group of heterocyclic specialized metabolites characterized by a core structure comprising a hexahydro‐1H‐pyrrolizine. PAs are synthesized through two main pathways. In plants, assembly occurs via a homospermidine synthase, and in bacteria, through combined action of a nonribosomal peptide synthetase and a Baeyer–Villiger monooxygenase. While the toxic properties of plant‐derived PAs and their prevalence in animal and human foods have been extensively studied, the biological roles and biosynthesis of more complex bacterial PAs are not well understood. Here, we report the identification and characterization of a bacterial biosynthetic gene cluster from Xenorhabdus hominickii, xhpA‐G, which is responsible for producing the PA pseudo‐dimer pyrrolizwilline. Analysis of X. hominickii promoter exchange mutants together with heterologous expression of xhpA‐G in E. coli, revealed a set of pathway intermediates, two of which were chemically synthesized, as well as multiple derivatives. This information was leveraged to propose a detailed biosynthetic pathway to pyrrolizwilline. Furthermore, we have characterized the hydrolase XhpG, the key enzyme in the conversion of the pathway intermediate pyrrolizixenamide to pyrrolizwilline, using X‐ray crystallography and small‐angle X‐ray scattering (SAXS). [ABSTRACT FROM AUTHOR]

Dithiolopyrrolone (DTP) natural products are produced by several different bacteria and have potent antibacterial, antifungal and anticancer activities. While the amide of their DTP core can be methylated to fine‐tune bioactivity, the enzyme responsible for the amide N‐methylation has remained elusive in most taxa. Here, we identified the amide methyltransferase XrdM that is responsible for xenorhabdin (XRD) methylation in Xenorhabdus doucetiae but encoded outside of the XRD gene cluster. XrdM turned out to be isofunctional with the recently reported methyltransferase DtpM, that is involved in the biosynthesis of the DTP thiolutin, although its X‐ray structure is unrelated to that of DtpM. To investigate the structural basis for ligand binding in both enzymes, we used X‐ray crystallography, modeling, site‐directed mutagenesis, and kinetic activity assays. Our study expands the limited knowledge of post‐non‐ribosomal peptide synthetase (NRPS) amide methylation in DTP biosynthesis and reveals an example of convergent evolution of two structurally completely different enzymes for the same reaction in different organisms. [ABSTRACT FROM AUTHOR]

BACKGROUND: In the perpetual struggle to manage mosquito populations, there has been increasing demand for the development of biopesticides to supplant/complement current products. The insecticidal potential of Xenorhabdus and Photorhabdus has long been recognized and is of interest for the control of important mosquitoes like Aedes albopictus which vectors over 20 different arboviruses of global public health concern. RESULTS: The larvicidal effects of cell‐free supernatants, cell growth cultures and cell mass of an extensive list of Xenorhabdus and Photorhabdus spp. was investigated. They were quite effective against Ae. albopictus causing larval mortality ranging between 52–100%. Three Photorhabdus spp. and 13 Xenorhabdus spp. release larvicidal compounds in cell‐free supernatants. Cell growth culture of all tested species exhibited larvicidal activity, except for Xenorhabdus sp. TS4. Twenty‐one Xenorhabdus and Photorhabdus bacterial cells (pellet) exhibited oral toxicity (59–91%) against exposed larvae. The effect of bacterial supernatants on the mosquito eggs were also assessed. Bacterial supernatants inhibited the hatching of mosquito eggs; when unhatched eggs were transferred to clean water, they all hatched. Using the easyPACId approach, the larvicidal compounds in bacterial supernatant were identified as fabclavine from X. szentirmaii and xencoumacin from X. nematophila (causing 98 and 70% mortality, respectively, after 48 h). Xenorhabdus cabanillasii and X. hominickii fabclavines were as effective as commercial Bacillus thuringiensis subsp. israelensis and spinosad products within 5 days post‐application (dpa). CONCLUSION: Fabclavine and xenocoumacin can be developed into novel biolarvicides, can be used as a model to synthesize other compounds or/and can be combined with other commercial biolarvicides. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The recently identified natural product NOSO‐95A from entomopathogenic Xenorhabdus bacteria, derived from a biosynthetic gene cluster (BGC) encoding a non‐ribosomal peptide synthetase (NRPS), was the first member of the odilorhabdin class of antibiotics. This class exhibits broad‐spectrum antibiotic activity and inspired the development of the synthetic derivative NOSO‐502, which holds potential as a new clinical drug by breaking antibiotic resistance. While the mode of action of odilorhabdins was broadly investigated, their biosynthesis pathway remained poorly understood. Here we describe the heterologous production of NOSO‐95A in Escherichia coli after refactoring the complete BGC. Since the production titer was low, NRPS engineering was applied to uncover the underlying biosynthetic principles. For this, modules of the odilorhabdin NRPS fused to other synthetases were co‐expressed with candidate hydroxylases encoded in the BGC allowing the characterization of the biosynthesis of three unusual amino acids and leading to the identification of a prodrug‐activation mechanism by deacylation. Our work demonstrates the application of NRPS engineering as a blueprint to mechanistically elucidate large or toxic NRPS and provides the basis to generate novel odilorhabdin analogues with improved properties in the future. [ABSTRACT FROM AUTHOR]

Pigments such as anthraquinones (AQs) and melanins are antioxidants, protectants, or virulence factors. AQs from the entomopathogenic bacterium Photorhabdus laumondii are produced by a modular type II polyketide synthase system. A key enzyme involved in AQ biosynthesis is PlAntI, which catalyzes the hydrolysis of the bicyclic‐intermediate‐loaded acyl carrier protein, polyketide trimming, and assembly of the aromatic AQ scaffold. Here, multiple crystal structures of PlAntI in various conformations and with bound substrate surrogates or inhibitors are reported. Structure‐based mutagenesis and activity assays provide experimental insights into the three sequential reaction steps to yield the natural product AQ‐256. For comparison, a series of ligand‐complex structures of two functionally related hydrolases involved in the biosynthesis of 1,8‐dihydroxynaphthalene‐melanin in pathogenic fungi is determined. These data provide fundamental insights into the mechanism of polyketide trimming that shapes pigments in pro‐ and eukaryotes. [ABSTRACT FROM AUTHOR]

Benzoxazolinate is a rare bis‐heterocyclic moiety that interacts with proteins and DNA and confers extraordinary bioactivities on natural products, such as C‐1027. However, the biosynthetic gene responsible for the key cyclization step of benzoxazolinate remains unclear. Herein, we show a putative acyl AMP‐ligase responsible for the last cyclization step. We used the enzyme as a probe for genome mining and discovered that the orphan benzobactin gene cluster in entomopathogenic bacteria prevails across Proteobacteria and Firmicutes. It turns out that Pseudomonas chlororaphis produces various benzobactins, whose biosynthesis is highlighted by a synergistic effect of two unclustered genes encoding enzymes on boosting benzobactin production; the formation of non‐proteinogenic 2‐hydroxymethylserine by a serine hydroxymethyltransferase; and the types I and II NRPS architecture for structural diversity. Our findings reveal the biosynthetic potential of a widespread benzobactin gene cluster. [ABSTRACT FROM AUTHOR]

Bacterial natural products in general, and non‐ribosomally synthesized peptides in particular, are structurally diverse and provide us with a broad range of pharmaceutically relevant bioactivities. Yet, traditional natural product research suffers from rediscovering the same scaffolds and has been stigmatized as inefficient, time‐, labour‐ and cost‐intensive. Combinatorial chemistry, on the other hand, can produce new molecules in greater numbers, cheaper and in less time than traditional natural product discovery, but also fails to meet current medical needs due to the limited biologically relevant chemical space that can be addressed. Consequently, methods for the high throughput generation of new natural products would offer a new approach to identifying novel bioactive chemical entities for the hit to lead phase of drug discovery programs. As a follow‐up to our previously published proof‐of‐principle study on generating bipartite type S non‐ribosomal peptide synthetases (NRPSs), we now envisaged the de novo generation of non‐ribosomal peptides (NRPs) on an unreached scale. Using synthetic zippers, we split NRPSs in up to three subunits and rapidly generated different bi‐ and tripartite NRPS libraries to produce 49 peptides, peptide derivatives, and de novo peptides at good titres up to 145 mg L−1. A further advantage of type S NRPSs not only is the possibility to easily expand the created libraries by re‐using previously created type S NRPS, but that functions of individual domains as well as domain‐domain interactions can be studied and assigned rapidly. [ABSTRACT FROM AUTHOR]

Non‐ribosomal peptide synthetases (NRPSs) are the origin of a wide range of natural products, including many clinically used drugs. Efficient engineering of these often giant biosynthetic machineries to produce novel non‐ribosomal peptides (NRPs) is an ongoing challenge. Here we describe a cloning and co‐expression strategy to functionally combine NRPS fragments of Gram‐negative and ‐positive origin, synthesising novel peptides at titres up to 220 mg L−1. Extending from the recently introduced definition of eXchange Units (XUs), we inserted synthetic zippers (SZs) to split single protein NRPSs into independently expressed and translated polypeptide chains. These synthetic type of NRPS (type S) enables easier access to engineering, overcomes cloning limitations, and provides a simple and rapid approach to building peptide libraries via the combination of different NRPS subunits. [ABSTRACT FROM AUTHOR]

Summary: Natural products can contribute to abiotic stress tolerance in plants and fungi. We hypothesize that biosynthetic gene clusters (BGCs), the genomic elements that underlie natural product biosynthesis, display structured differences along elevation gradients. We analysed biosynthetic gene variation in natural populations of the lichen‐forming fungus Umbilicaria pustulata. We collected a total of 600 individuals from the Mediterranean and cold‐temperate climates. Population genomic analyses indicate that U. pustulata contains three clusters that are highly differentiated between the Mediterranean and cold‐temperate populations. One entire cluster is exclusively present in cold‐temperate populations, and a second cluster is putatively dysfunctional in all cold‐temperate populations. In the third cluster variation is fixed in all cold‐temperate populations due to hitchhiking. In these two clusters the presence of consistent allele frequency differences among replicate populations/gradients suggests that selection rather than drift is driving the pattern. We advocate that the landscape of fungal biosynthetic genes is shaped by both positive and hitchhiking selection. We demonstrate, for the first time, the presence of climate‐associated BGCs and BGC variations in lichen‐forming fungi. While the associated secondary metabolites of the candidate clusters are presently unknown, our study paves the way for targeted discovery of natural products with ecological significance. [ABSTRACT FROM AUTHOR]

Non‐ribosomal peptide synthetases (NRPS) produce natural products from amino acid building blocks. They often consist of multiple polypeptide chains which assemble in a specific linear order via specialized N‐ and C‐terminal docking domains (N/CDDs). Typically, docking domains function independently from other domains in NRPS assembly. Thus, docking domain replacements enable the assembly of "designer" NRPS from proteins that normally do not interact. The multiprotein "peptide‐antimicrobial‐Xenorhabdus" (PAX) peptide‐producing PaxS NRPS is assembled from the three proteins PaxA, PaxB and PaxC. Herein, we show that the small CDD of PaxA cooperates with its preceding thiolation (T1) domain to bind the NDD of PaxB with very high affinity, establishing a structural and thermodynamical basis for this unprecedented docking interaction, and we test its functional importance in vivo in a truncated PaxS assembly line. Similar docking interactions are apparently present in other NRPS systems. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Indolyloxazole alkaloids occur in diverse micro‐ and macroorganisms and exhibit a wide range of pharmacological activities. Despite their ubiquitous occurrence and simple structures, the biosynthetic pathway remained unknown. Here, we used transposon mutagenesis in the labradorin producer Pseudomonas entomophila to identify a cryptic biosynthetic locus encoding an N‐acyltransferase and a non‐heme diiron desaturase‐like enzyme. Heterologous expression in E. coli demonstrates that both enzymes are sufficient to produce indolyloxazoles. Probing their function in stable‐isotope feeding experiments, we provide evidence for an unusual desaturase mechanism that generates the oxazole by decarboxylative cyclization. [ABSTRACT FROM AUTHOR]

The interaction in multisubunit non‐ribosomal peptide synthetases (NRPSs) is mediated by docking domains that ensure the correct subunit‐to‐subunit interaction. We introduced natural docking domains into the three‐module xefoampeptide synthetase (XfpS) to create two to three artificial NRPS XfpS subunits. The enzymatic performance of the split biosynthesis was measured by absolute quantification of the products by HPLC‐ESI‐MS. The connecting role of the docking domains was probed by deleting integral parts of them. The peptide production data was compared to soluble protein amounts of the NRPS using SDS‐PAGE. Reduced peptide synthesis was not a result of reduced soluble NRPS concentration but a consequence of the deletion of vital docking domain parts. Splitting the xefoampeptide biosynthesis polypeptide by introducing docking domains was feasible and resulted in higher amounts of product in one of the two tested split‐module cases compared to the full‐length wild‐type enzyme. [ABSTRACT FROM AUTHOR]

Summary: Bacteria of the genera Photorhabdus and Xenorhabdus produce a plethora of natural products to support their similar symbiotic life cycles. For many of these compounds, the specific bioactivities are unknown. One common challenge in natural product research when trying to prioritize research efforts is the rediscovery of identical (or highly similar) compounds from different strains. Linking genome sequence to metabolite production can help in overcoming this problem. However, sequences are typically not available for entire collections of organisms. Here, we perform a comprehensive metabolic screening using HPLC‐MS data associated with a 114‐strain collection (58 Photorhabdus and 56 Xenorhabdus) across Thailand and explore the metabolic variation among the strains, matched with several abiotic factors. We utilize machine learning in order to rank the importance of individual metabolites in determining all given metadata. With this approach, we were able to prioritize metabolites in the context of natural product investigations, leading to the identification of previously unknown compounds. The top three highest ranking features were associated with Xenorhabdus and attributed to the same chemical entity, cyclo(tetrahydroxybutyrate). This work also addresses the need for prioritization in high‐throughput metabolomic studies and demonstrates the viability of such an approach in future research. [ABSTRACT FROM AUTHOR]

Abstract: Photorhabdus luminescens dedicates a significant proportion of its genome to the production of natural products. These products and the structural variation in their derivatives may occur by a number of well‐described mechanisms, such as module skipping or precursor promiscuity. Cappable‐seq was used to identify transcriptional start sites of many of the gene clusters present in P. luminescens TTO1. We discovered that variations associated with the non‐ribosomal peptide synthetase Kol, which is responsible for kolossin A production, possessed a number of internal transcripts that lead to synthesis of the smaller kolossin derivatives kolossin B and C. The data here support a new mechanism of natural product biosynthetic variation whereby mRNA may code for shorter NRPS enzymes in addition to full‐length proteins, resulting in the production of smaller peptide derivatives. [ABSTRACT FROM AUTHOR]

Summary: Fungi are prolific producers of natural products routinely screened for biotechnological applications, and those living endophytically within plants attract particular attention because of their purported chemical diversity. However, the harnessing of their biosynthetic potential is hampered by a large and often cryptic phylogenetic and ecological diversity, coupled with a lack of large‐scale natural products' dereplication studies. To guide efforts to discover new chemistries among root‐endophytic fungi, we analyzed the natural products produced by 822 strains using an untargeted UPLC‐ESI‐MS/MS‐based approach and linked the patterns of chemical features to fungal lineages. We detected 17 809 compounds of which 7951 were classified in 1992 molecular families, whereas the remaining were considered unique chemistries. Our approach allowed to annotate 1191 compounds with different degrees of accuracy, many of which had known fungal origins. Approximately 61% of the compounds were specific of a fungal order, and differences were observed across lineages in the diversity and characteristics of their chemistries. Chemical profiles also showed variable chemosystematic values across lineages, ranging from relative homogeneity to high heterogeneity among related fungi. Our results provide an extensive resource to dereplicate fungal natural products and may assist future discovery programs by providing a guide for the selection of target fungi. [ABSTRACT FROM AUTHOR]

Xenorhabdus doucetiae, the bacterial symbiont of the entomopathogenic nematode Steinernema diaprepesi produces several different fatty acid amides. Their biosynthesis has been studied using a combination of analysis of gene deletions and promoter exchanges in X. doucetiae and heterologous expression of candidate genes in E. coli. While a decarboxylase is required for the formation of all observed phenylethylamides and tryptamides, the acyltransferase XrdE encoded in the xenorhabdin biosynthesis gene cluster is responsible for the formation of short chain acyl amides. Additionally, new, long-chain and cytotoxic acyl amides were identified in X. doucetiae infected insects and when X. doucetiae was grown in Galleria Instant Broth (GIB). When the bioactivity of selected amides was tested, a quorum sensing modulating activity was observed for the short chain acyl amides against the two different quorum sensing systems from Chromobacterium and Janthinobacterium. [ABSTRACT FROM AUTHOR]

Effective iron acquisition and fine-tuned intracellular iron storage systems are the main prerequisites for a successful host invasion by a pathogen. Bacteria have developed several different strategies to sequester this essential element from their environment, one relies on the secretion of low molecular weight compounds with high affinity for ferric iron, the so-called siderophores. Here, we report hydroxamate siderophore structures produced by entomopathogenic bacteria of the species Xenorhabdus and Photorhabdus, which are known for their potential to produce bioactive natural products, required for their role as nematode symbiont and insect pathogen. Four siderophores could be identified, namely aerobactin, putrebactin, avaroferrin and ochrobactin C, which was found previously only in marine bacteria. While the putrebactin and avaroferrin producing biosynthesis gene cluster (BGC) is more widespread and most likely was present in a common ancestor of these bacteria, the aerobactin and ochrobactin producing BGC was probably taken up by a few strains individually. For aerobactin a role in virulence towards Galleria mellonella larvae is shown. [ABSTRACT FROM AUTHOR]

The natural products isatropolone A-C ( 1- 3) were reisolated from Streptomyces Gö66, with 1 and 3 showing potent activity against Leishmania donovani. They contain a rare tropolone ring derived from a type II polyketide biosynthesis pathway. Their biosynthesis was elucidated by labeling experiments, analysis of the biosynthesis gene cluster, its partial heterologous expression, and structural characterization of various intermediates. Owing to their 1,5-diketone moiety, they can react with ammonia, amines, lysine, and lysine-containing peptides and proteins, which results in the formation of a covalent bond and subsequent pyridine ring formation. Their fluorescence properties change upon amine binding, enabling the simple visualization of reacted amines including proteins. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Photorhabdus luminescens maintains a symbiotic relationship with the nematodes Heterorhabditis bacteriophora and together they infect and kill insect larvae. To maintain this symbiotic relationship, the bacteria must produce an array of secondary metabolites to assist in the development and replication of nematodes. The regulatory mechanisms surrounding production of these compounds are mostly unknown. The global post-transcriptional regulator, Hfq, is widespread in bacteria and performs many functions, one of which is the facilitation of sRNA binding to target mRNAs, with recent research thoroughly exploring its various pleiotropic effects. Here we generate and characterize an hfq deletion mutant and show that in the absence of hfq, the bacteria are no longer able to maintain a healthy symbiosis with nematodes due to the abolishment of the production of all known secondary metabolites. RNAseq led us to produce a second deletion of a known repressor, HexA, in the same strain, which restored both metabolite production and symbiosis. [ABSTRACT FROM AUTHOR]

Many methods have been devised over the decades to trace precursors of specific molecules in cellular environments as, for example, in biosynthesis studies. The advent of click chemistry has facilitated the powerful combination of tracing and at the same time sieving the highly complex metabolome for compounds derived from simple or complex starting materials, especially when the click reaction takes place on a solid support. While the principle of solid-phase click reactions has already been successfully applied for selective protein and peptide enrichment, the successful enrichment of much smaller primary and secondary metabolites, showing great structural diversity and undergoing many different biosynthetic steps, has seen only little development. For bacterial secondary metabolism, a far broader tolerance for 'clickable' precursors was observed than in ribosomal proteinogenesis, thus making this method a surprisingly valuable tool for the tracking and discovery of compounds within the cellular biochemical network. The implementation of this method has led to the identification of several new compounds from the bacterial genera Photorhabdus and Xenorhabdus, clearly proving its power. [ABSTRACT FROM AUTHOR]

Pyrrolizidine alkaloids (PAs) are widespread plant natural products with potent toxicity and bioactivity. Herein, the identification of bacterial PAs from entomopathogenic bacteria using differential analysis by 2D NMR spectroscopy (DANS) and mass spectrometry is described. Their biosynthesis was elucidated to involve a non-ribosomal peptide synthetase. The occurrence of these biosynthesis gene clusters in Gram-negative and Gram-positive bacteria indicates an important biological function in bacteria. [ABSTRACT FROM AUTHOR]

Despite the importance of microbial natural products for human health, only a few bacterial genera have been mined for the new natural products needed to overcome the urgent threat of antibiotic resistance. This is surprising, given that genome sequencing projects have revealed that the capability to produce natural products is not a rare feature among bacteria. Even the bacteria occurring in the human microbiome produce potent antibiotics, and thus potentially are an untapped resource for novel compounds, potentially with new activities. This review highlights examples of bacteria that should be considered new sources of natural products, including anaerobes, pathogens, and symbionts of humans, insects, and nematodes. Exploitation of these producer strains, combined with advances in modern natural product research methodology, has the potential to open the way for a new golden age of microbial therapeutics. [ABSTRACT FROM AUTHOR]

Bakterien, die in und auf uns leben, beeinflussen unsere Gesundheit massiv und wurden in ihrer Bedeutung bisher unterschätzt. Dazu gehört auch die Produktion niedermolekularer Naturstoffe durch „unsere”︁ Bakterien, die sowohl chemisch als auch biologisch sehr interessant sein können, wie es der Wettlauf um die Biosynthese und Struktur des Colibactins, einer genotoxischen Substanz aus einem humanen Darmbakterium, beweist. [ABSTRACT FROM AUTHOR]

Gut reaction: There is increasing evidence that the impact on human health and disease of the microbes living in and on us has been underestimated. Several of the small molecules produced by “our” bacteria are structurally highly complex and show unusual biosynthetic pathways or modes of action, as highlighted by the race to elucidate the structure and biosynthesis of colibactin, a genotoxic compound produced by human gut bacteria. [ABSTRACT FROM AUTHOR]

Es wird die bislang größte zusammenhängende bakterielle nicht ‐ ribosomale Peptidsynthetase (NRPS) beschrieben, die aus 15 konsekutiven Modulen besteht und aus einem einzigen voll funktionalen Gen des entomopathogenen Bakteriums Photorhabdus luminescens hervorgeht. Die Identifikation ihres kryptischen Biosyntheseprodukts wurde mithilfe einer Kombination aus Genomanalyse, Promotoraustausch, Isotopenmarkierung und Totalsynthese einer fokussierten Sammlung von Peptidkandidaten erreicht. Obwohl zur wachsenden Klasse der D ‐ /L ‐ Peptid ‐ Naturstoffe zählend, wies der produzierte Metabolit Kolossin A keine nennenswerte antibakterielle Aktivität auf und ist möglicherweise an einer Interspeziesinteraktion beteiligt. Ein Stereoisomer des ungewöhnlichen Naturstoffs zeigte hohe Aktivität gegen Trypanosoma brucei rhodesiense, einen hartnäckigen Parasiten, der die tödliche afrikanische Schlafkrankheit verursacht. Ein schlafender Riese: Im entomopathogenen Bakterium Photorhabdus luminescens wurde eine einzelne nicht ‐ ribosomale Peptidsynthetase von 1.8 MDa gefunden und ihre Bildung gezielt aktiviert. Das 15 ‐ mere D ‐ /L ‐ Peptidprodukt dieser Biosynthese wurde durch Kombination von Genomanalyse des stillen Genclusters, Molekularbiologie, LC ‐ MS und Totalsynthese charakterisiert. Ein Stereoisomer von Kolossin A ist aktiv gegen den Erreger der afrikanischen Schlafkrankheit. [ABSTRACT FROM AUTHOR]

The largest continuous bacterial nonribosomal peptide synthetase discovered so far is described. It consists of 15 consecutive modules arising from an uninterrupted, fully functional gene in the entomopathogenic bacterium Photorhabdus luminescens. The identification of its cryptic biosynthesis product was achieved by using a combination of genome analysis, promoter exchange, isotopic labeling experiments, and total synthesis of a focused collection of peptide candidates. Although it belongs to the growing class of D-/ L-peptide natural products, the encoded metabolite kolossin A was found to be largely devoid of antibiotic activity and is likely involved in interspecies communication. A stereoisomer of this peculiar natural product displayed high activity against Trypanosoma brucei rhodesiense, a recalcitrant parasite that causes the deadly disease African sleeping sickness. [ABSTRACT FROM AUTHOR]

Six new lipodepsipeptides and an additional linear derivative named taxlllaids A-G ( 1- 7) have been identified in the entomopathogenic bacterium Xenorhabdus indica. The structures of the main compounds have been solved by detailed NMR spectroscopic analysis and the structures of minor derivatives were elucidated by a combination of labelling experiments and detailed MS experiments. The absolute configuration of the taxlllaids was deduced by using the advanced Marfey method and analysis of the biosynthesis gene cluster showing the presence of epimerisation domains, which was subsequently proved to be correct by solid-phase peptide synthesis of all taxlllaids. The exchange of a single amino acid in the adenylation domain was shown to be responsible for substrate promiscuity of the third A domain, resulting in the incorporation of leucine, phenylalanine or tyrosine. Bioactivity testing revealed the taxlllaids to be weakly active against Plasmodium falciparum and against a number of eukaryotic cell lines. [ABSTRACT FROM AUTHOR]

PoyD is a radical S-adenosyl methionine epimerase that introduces multiple D-configured amino acids at alternating positions into the highly complex marine peptides polytheonamide A and B. This novel post-translational modification contributes to the ability of the polytheonamides to form unimolecular minimalistic ion channels and its cytotoxic activity at picomolar levels. Using a genome mining approach we have identified additional PoyD homologues in various bacteria. Three enzymes were expressed in E. coli with their cognate as well as engineered peptide precursors and shown to introduce diverse D-amino acid patterns into all- L peptides. The data reveal a family of architecturally and functionally distinct enzymes that exhibit high regioselectivity, substrate promiscuity, and irreversible action and thus provide attractive opportunities for peptide engineering. [ABSTRACT FROM AUTHOR]

Bacteria from the Bacteroidetes phylum are known producers of the chemotaxonomic relevant flexirubins. These orange pigments comprise a non-isoprenoid aryl-polyene carboxylic acid esterified with a dialkylresorcinol. Herein, we report a gene cluster from Chitinophaga pinensis encoding the biosynthesis of the polyene moiety and the biochemical characterization of a tyrosine ammonia-lyase and a 4-coumarate-CoA ligase responsible for the initiation of the polyene biosynthesis. Additionally, the flexirubin of C. pinensis was characterized by a combination of feeding experiments, high-performance liquid chromatography tandem mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry. [ABSTRACT FROM AUTHOR]

During the search for novel natural products from entomopathogenic Xenorhabdus doucetiae DSM17909 and X. mauleonii DSM17908 novel peptides named xenoamicins were identified in addition to the already known antibiotics xenocoumacin and xenorhabdin. Xenoamicins are acylated tridecadepsipeptides consisting of mainly hydrophobic amino acids. The main derivative xenoamicin A ( 1) was isolated from X. mauleonii DSM17908, and its structure elucidated by detailed 1 D and 2 D NMR experiments. Detailed MS experiments, also in combination with labeling experiments, confirmed the determined structure and allowed structure elucidation of additional derivatives. Moreover, the xenoamicin biosynthesis gene cluster was identified and analyzed in X. doucetiae DSM17909, and its participation in xenoamicin biosynthesis was confirmed by mutagenesis. Advanced Marfey's analysis of 1 showed that the absolute configuration of the amino acids is in agreement with the predicted stereochemistry deduced from the nonribosomal peptide synthetase XabABCD. Biological testing revealed activity of 1 against Plasmodium falciparum and other neglected tropical diseases but no antibacterial activity. [ABSTRACT FROM AUTHOR]