Phytoplankton trigger the production of cryptic metabolites in the marine actinobacteria Salinispora tropica

AbstractBacteria from the Actinomycete family are a remarkable source of natural products with pharmaceutical potential. The discovery of novel molecules from these organisms is, however, hindered because most of the biosynthetic gene clusters (BGCs) encoding these secondary metabolites are cryptic or silent and are referred to as orphan BGCs. While co-culture has proven to be a promising approach to unlock the biosynthetic potential of many microorganisms by activating the expression of these orphan BGCs, it still remains an underexplored technique. The marine actinobacteria Salinispora tropica, for instance, produces valuable compounds such as the anti-cancer molecule salinosporamide A but half of its putative BGCs are still orphan. Although previous studies have looked into using marine heterotrophs to induce orphan BGCs in Salinispora, the potential impact of co-culturing marine phototrophs with Salinispora has yet to be investigated. Following the observation of clear antimicrobial phenotype of the actinobacterium on a range of phytoplanktonic organisms, we here report the discovery of novel cryptic secondary metabolites produced by S. tropica in response to its co-culture with photosynthetic primary producers. An approach combining metabolomics and proteomics revealed that the photosynthate released by phytoplankton influences the biosynthetic capacities of S. tropica with both production of new molecules and the activation of orphan BGCs. Our work pioneers the use of phototrophs as a promising strategy to accelerate the discovery of novel natural products from actinobacteria.ImportanceThe alarming increase of antimicrobial resistance has generated an enormous interest in the discovery of novel active compounds. The isolation of new microbes to untap novel natural products is currently hampered because most biosynthetic gene clusters (BGC) encoded by these microorganisms are not expressed under standard laboratory conditions, i.e. mono-cultures. Here we show that co-culturing can be an easy way for triggering silent BGC. By combining state-of-the-art metabolomics and high-throughput proteomics, we characterized the activation of cryptic metabolites and silent biosynthetic gene clusters in the marine actinobacteria Salinispora tropica by the presence of phytoplankton photosynthate. We further suggest a mechanistic understanding of the antimicrobial effect this actinobacterium has on a broad range of prokaryotic and eukaryotic phytoplankton species and reveal a promising candidate for antibiotic production.

Download Full-text

New Approaches to Detect Biosynthetic Gene Clusters in the Environment

Medicines ◽

10.3390/medicines6010032 ◽

2019 ◽

Vol 6 (1) ◽

pp. 32 ◽

Cited By ~ 7

Author(s):

Ray Chen ◽

Hon Wong ◽

Brendan Burns

Keyword(s):

Natural Products ◽

Secondary Metabolites ◽

Gene Clusters ◽

Screening Methods ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Diverse Range ◽

Bioinformatic Tools ◽

Culture Independent ◽

Traditional Approaches

Microorganisms in the environment can produce a diverse range of secondary metabolites (SM), which are also known as natural products. Bioactive SMs have been crucial in the development of antibiotics and can also act as useful compounds in the biotechnology industry. These natural products are encoded by an extensive range of biosynthetic gene clusters (BGCs). The developments in omics technologies and bioinformatic tools are contributing to a paradigm shift from traditional culturing and screening methods to bioinformatic tools and genomics to uncover BGCs that were previously unknown or transcriptionally silent. Natural product discovery using bioinformatics and omics workflow in the environment has demonstrated an extensive distribution of BGCs in various environments, such as soil, aquatic ecosystems and host microbiome environments. Computational tools provide a feasible and culture-independent route to find new secondary metabolites where traditional approaches cannot. This review will highlight some of the advances in the approaches, primarily bioinformatic, in identifying new BGCs, especially in environments where microorganisms are rarely cultured. This has allowed us to tap into the huge potential of microbial dark matter.

Download Full-text

Understanding the evolutionary origins of bacterial natural products with immunosuppressant properties

10.7287/peerj.preprints.27774v1 ◽

2019 ◽

Author(s):

Wenfa Ng

Keyword(s):

Natural Products ◽

Secondary Metabolites ◽

Secondary Metabolite ◽

Human Body ◽

Immune Cells ◽

Bacterial Species ◽

Gene Clusters ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Drug Candidates

Actinobacteria and streptomyces are known to produce a variety of natural products, some of which confer antibiotic or immunosuppressive activities. While it is understandable that microbes develop the ability to synthesize molecules such as antibiotics that attack other competing microbes, but why would a secondary metabolite (natural product) synthesized by a microbe confer immunosuppressive activities? Was the capability to synthesize such a molecule endowed by evolution in the context of enabling microbes to develop resistance to immune cells of the human body? Or did the capability come from the need to colonize human body surfaces or gut to gain a survival niche for the microbe? Given that actinobacteria and streptomyces are soil microbes not usually associated with human body surfaces, could their biosynthetic capability for particular immunosuppressants arise from horizontal gene transfer from bacteria that colonize human body surfaces and subsequently develop the ability to synthesize the pertinent compounds through evolution? An alternate line of thinking on this issue touches on the possibility that microbes could encounter analogs of immuno-active molecules in their natural environment. Such molecules might elicit undesired physiological effects on the microbes, which place a selection pressure on microbes to develop countermeasures to the immuno-active molecules through mutations. Hence, through evolution, microbes could have developed the capability to synthesize secondary metabolites able to bind analogs of immuno-active molecules and help sequester them or quench their bioactivity. Subsequent profiling of such secondary metabolites in drug discovery efforts could have uncovered compounds with immunosuppressant activity which are originally developed for counteracting analogs of immuno-active molecules in the environment. It has to be recognized that analogs of immuno-active compounds remain somewhat dissimilar to immune compounds secreted by human immune cells, but they likely share common motifs for protein-secondary metabolite interactions. Direct evidence of the evolution of natural products with immunosuppressant activities could only be obtained from challenging suitable bacterial species with immuno-active molecules. Long cultivation experiments with multiple generations may result in the evolution of biosynthetic gene clusters for the synthesis of natural products able to sequester or quench immuno-active molecules. But, on the another hand, understanding relative binding affinities between a library of natural products and immuno-active molecules from humans would suggest drug candidates and their biosynthetic gene clusters. Subsequent phylogenetic analysis of cluster genes with their homologs from other species may yield insights into the evolution of genes and their putative function.

Download Full-text

Enhypyrazinones A and B, Pyrazinone Natural Products from a Marine-Derived Myxobacterium Enhygromyxa sp.

Marine Drugs ◽

10.3390/md17120698 ◽

2019 ◽

Vol 17 (12) ◽

pp. 698 ◽

Cited By ~ 1

Author(s):

Fan Zhang ◽

Doug R. Braun ◽

Scott R. Rajski ◽

Don DeMaria ◽

Tim S. Bugni

Keyword(s):

Natural Products ◽

Secondary Metabolites ◽

Biological Activities ◽

Gene Clusters ◽

Structural Features ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Data Analyses ◽

Nmr Data ◽

Immense Potential

To date, studies describing myxobacterial secondary metabolites have been relatively scarce in comparison to those addressing actinobacterial secondary metabolites. This realization suggests the immense potential of myxobacteria as an intriguing source of secondary metabolites with unusual structural features and a wide array of biological activities. Marine-derived myxobacteria are especially attractive due to their unique biosynthetic gene clusters, although they are more difficult to handle than terrestrial myxobacteria. Here, we report the discovery of two new pyrazinone-type molecules, enhypyrazinones A and B, from a marine-derived myxobacterium Enhygromyxa sp. Their structures were elucidated by HRESIMS and comprehensive NMR data analyses. Compounds 1 and 2, which contain a rare trisubstituted-pyrazinone core, represent a unique class of molecules from Enhygromyxa sp.

Download Full-text

SeMPI 2.0—A Web Server for PKS and NRPS Predictions Combined with Metabolite Screening in Natural Product Databases

Metabolites ◽

10.3390/metabo11010013 ◽

2020 ◽

Vol 11 (1) ◽

pp. 13

Author(s):

Paul F. Zierep ◽

Adriana T. Ceci ◽

Ilia Dobrusin ◽

Sinclair C. Rockwell-Kollmann ◽

Stefan Günther

Keyword(s):

Natural Products ◽

Secondary Metabolites ◽

Building Block ◽

Web Server ◽

Gene Clusters ◽

Type I ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

A Genome ◽

Wide Range

Microorganisms produce secondary metabolites with a remarkable range of bioactive properties. The constantly increasing amount of published genomic data provides the opportunity for efficient identification of biosynthetic gene clusters by genome mining. On the other hand, for many natural products with resolved structures, the encoding biosynthetic gene clusters have not been identified yet. Of those secondary metabolites, the scaffolds of nonribosomal peptides and polyketides (type I modular) can be predicted due to their building block-like assembly. SeMPI v2 provides a comprehensive prediction pipeline, which includes the screening of the scaffold in publicly available natural compound databases. The screening algorithm was designed to detect homologous structures even for partial, incomplete clusters. The pipeline allows linking of gene clusters to known natural products and therefore also provides a metric to estimate the novelty of the cluster if a matching scaffold cannot be found. Whereas currently available tools attempt to provide comprehensive information about a wide range of gene clusters, SeMPI v2 aims to focus on precise predictions. Therefore, the cluster detection algorithm, including building block generation and domain substrate prediction, was thoroughly refined and benchmarked, to provide high-quality scaffold predictions. In a benchmark based on 559 gene clusters, SeMPI v2 achieved comparable or better results than antiSMASH v5. Additionally, the SeMPI v2 web server provides features that can help to further investigate a submitted gene cluster, such as the incorporation of a genome browser, and the possibility to modify a predicted scaffold in a workbench before the database screening.

Download Full-text

Understanding the evolutionary origins of bacterial natural products with immunosuppressant properties

10.7287/peerj.preprints.27774 ◽

2019 ◽

Author(s):

Wenfa Ng

Keyword(s):

Natural Products ◽

Secondary Metabolites ◽

Secondary Metabolite ◽

Human Body ◽

Immune Cells ◽

Bacterial Species ◽

Gene Clusters ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Drug Candidates

Download Full-text

Genomic and transcriptomic survey of an endophytic fungus Calcarisporium arbuscula NRRL 3705 and potential overview of its secondary metabolites

10.21203/rs.2.16691/v3 ◽

2020 ◽

Author(s):

Jintao Cheng ◽

Fei Cao ◽

Xinai Chen ◽

Yongquan Li ◽

Xuming Mao

Keyword(s):

Natural Products ◽

Secondary Metabolites ◽

Gene Cluster ◽

Secondary Metabolite ◽

Endophytic Fungi ◽

Endophytic Fungus ◽

Housekeeping Genes ◽

Gene Clusters ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters

Abstract Background: Secondary metabolites as natural products from endophytic fungi are important sources of pharmaceuticals. However, there is currently little understanding of endophytic fungi at the omics levels about their potential in secondary metabolites. Calcarisporium arbuscula , an endophytic fungus from the fruit bodies of Russulaceae, produces a variety of secondary metabolites with anti-cancer, anti-nematode and antibiotic activities. A comprehensive survey of the genome and transcriptome of this endophytic fungus will help to understand its capacity to biosynthesize secondary metabolites and will lay the foundation for the development of this precious resource. Results: In this study, we reported the high-quality genome sequence of C. arbuscula NRRL 3705 based on Single Molecule Real-Time sequencing technology. The genome of this fungus is over 45 Mb in size, larger than other typical filamentous fungi, and comprises 10,001 predicted genes, encoding at least 762 secretory-proteins, 386 carbohydrate-active enzymes and 177 P450 enzymes. 398 virulence factors and 228 genes related to pathogen-host interactions were also predicted in this fungus. Moreover , 65 secondary metabolite biosynthetic gene clusters were revealed, including the gene cluster for the mycotoxin aurovertins. In addition, several gene clusters were predicted to produce mycotoxins, including aflatoxin, alternariol, destruxin, citrinin and isoflavipucine. Notably, two independent gene clusters were shown that are potentially involved in thebiosynthesis of alternariol. Furthermore, RNA-Seq assays showed that only expression of the aurovertin gene cluster is much stronger than expression of the housekeeping genes under laboratory conditions, consistent with the observation that aurovertins are the predominant metabolites. Gene expression of the remaining 64 gene clusters for compound backbone biosynthesis was all lower than expression of the housekeeping genes, which partially explained poor production of other secondary metabolites in this fungus. Conclusions : Our omics data, along with bioinformatics analysis, indicated that C. arbuscula NRRL 3705 contains a large number of biosynthetic gene clusters and has a huge potential to produce a profound number of secondary metabolites. This work also provides the basis for development of endophytic fungi as a new resource of natural products with promising biological activities. Keywords: Endophytic Fungus, Calcarisporium arbuscula , Genome, Transcriptome, Secondary Metabolite

Download Full-text

Expanding the Natural Products Heterologous Expression Repertoire in the Model Cyanobacterium Anabaena sp. Strain PCC 7120: Production of Pendolmycin and Teleocidin B-4

10.26434/chemrxiv.11316098.v1 ◽

2019 ◽

Cited By ~ 1

Author(s):

Patrick Videau ◽

Kaitlyn Wells ◽

Arun Singh ◽

Jessie Eiting ◽

Philip Proteau ◽

...

Keyword(s):

Natural Products ◽

Genome Mining ◽

Gene Clusters ◽

Combinatorial Biosynthesis ◽

Test Case ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Cyanobacterium Anabaena ◽

Anabaena Sp ◽

Pcc 7120

Cyanobacteria are prolific producers of natural products and genome mining has shown that many orphan biosynthetic gene clusters can be found in sequenced cyanobacterial genomes. New tools and methodologies are required to investigate these biosynthetic gene clusters and here we present the use of <i>Anabaena </i>sp. strain PCC 7120 as a host for combinatorial biosynthesis of natural products using the indolactam natural products (lyngbyatoxin A, pendolmycin, and teleocidin B-4) as a test case. We were able to successfully produce all three compounds using codon optimized genes from Actinobacteria. We also introduce a new plasmid backbone based on the native <i>Anabaena</i>7120 plasmid pCC7120ζ and show that production of teleocidin B-4 can be accomplished using a two-plasmid system, which can be introduced by co-conjugation.

Download Full-text

Global biogeographic sampling of bacterial secondary metabolism

eLife ◽

10.7554/elife.05048 ◽

2015 ◽

Vol 4 ◽

Cited By ~ 74

Author(s):

Zachary Charlop-Powers ◽

Jeremy G Owen ◽

Boojala Vijay B Reddy ◽

Melinda A Ternei ◽

Denise O Guimarães ◽

...

Keyword(s):

Secondary Metabolites ◽

Genome Sequencing ◽

Geographic Distance ◽

Gene Clusters ◽

Natural World ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Road Map ◽

Two Factors ◽

Natural Products Discovery

Recent bacterial (meta)genome sequencing efforts suggest the existence of an enormous untapped reservoir of natural-product-encoding biosynthetic gene clusters in the environment. Here we use the pyro-sequencing of PCR amplicons derived from both nonribosomal peptide adenylation domains and polyketide ketosynthase domains to compare biosynthetic diversity in soil microbiomes from around the globe. We see large differences in domain populations from all except the most proximal and biome-similar samples, suggesting that most microbiomes will encode largely distinct collections of bacterial secondary metabolites. Our data indicate a correlation between two factors, geographic distance and biome-type, and the biosynthetic diversity found in soil environments. By assigning reads to known gene clusters we identify hotspots of biomedically relevant biosynthetic diversity. These observations not only provide new insights into the natural world, they also provide a road map for guiding future natural products discovery efforts.

Download Full-text

Identification of a New Antimicrobial, Desertomycin H, Utilizing a Modified Crowded Plate Technique

Marine Drugs ◽

10.3390/md19080424 ◽

2021 ◽

Vol 19 (8) ◽

pp. 424

Author(s):

Osama G. Mohamed ◽

Sadaf Dorandish ◽

Rebecca Lindow ◽

Megan Steltz ◽

Ifrah Shoukat ◽

...

Keyword(s):

Antibiotic Production ◽

Gene Clusters ◽

Multidrug Resistant ◽

Microbial Interactions ◽

Mass Spectrometry Data ◽

Metagenomic Data ◽

Resistant Bacteria ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Plate Technique

The antibiotic-resistant bacteria-associated infections are a major global healthcare threat. New classes of antimicrobial compounds are urgently needed as the frequency of infections caused by multidrug-resistant microbes continues to rise. Recent metagenomic data have demonstrated that there is still biosynthetic potential encoded in but transcriptionally silent in cultivatable bacterial genomes. However, the culture conditions required to identify and express silent biosynthetic gene clusters that yield natural products with antimicrobial activity are largely unknown. Here, we describe a new antibiotic discovery scheme, dubbed the modified crowded plate technique (mCPT), that utilizes complex microbial interactions to elicit antimicrobial production from otherwise silent biosynthetic gene clusters. Using the mCPT as part of the antibiotic crowdsourcing educational program Tiny Earth®, we isolated over 1400 antibiotic-producing microbes, including 62, showing activity against multidrug-resistant pathogens. The natural product extracts generated from six microbial isolates showed potent activity against vancomycin-intermediate resistant Staphylococcus aureus. We utilized a targeted approach that coupled mass spectrometry data with bioactivity, yielding a new macrolactone class of metabolite, desertomycin H. In this study, we successfully demonstrate a concept that significantly increased our ability to quickly and efficiently identify microbes capable of the silent antibiotic production.

Download Full-text