Identification of a New Antimicrobial, Desertomycin H, Utilizing a Modified Crowded 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.

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The Antibiotic Andrimid Produced by Vibrio coralliilyticus Increases Expression of Biosynthetic Gene Clusters and Antibiotic Production in Photobacterium galatheae

Frontiers in Microbiology ◽

10.3389/fmicb.2020.622055 ◽

2020 ◽

Vol 11 ◽

Author(s):

Yannick Buijs ◽

Thomas Isbrandt ◽

Sheng-Da Zhang ◽

Thomas Ostenfeld Larsen ◽

Lone Gram

Keyword(s):

Stress Response ◽

Antibiotic Production ◽

Gene Clusters ◽

Multidrug Resistant ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Gene Encoding ◽

Chemical Measurements ◽

Low Concentrations ◽

Vibrio Coralliilyticus

The development and spread of multidrug resistant pathogens have reinforced the urgency to find novel natural products with antibiotic activity. In bacteria, orphan biosynthetic gene clusters (BGCs) far outnumber the BGCs for which chemistry is known, possibly because they are transcriptionally silent under laboratory conditions. A strategy to trigger the production of this biosynthetic potential is to challenge the microorganism with low concentrations of antibiotics, and by using a Burkholderia genetic reporter strain (Seyedsayamdost, Proc Natl Acad Sci 111:7266–7271), we found BGC unsilencing activity for the antimicrobial andrimid, produced by the marine bacterium Vibrio coralliilyticus. Next, we challenged another marine Vibrionaceae, Photobacterium galatheae, carrier of seven orphan BGCs with sub-inhibitory concentrations of andrimid. A combined approach of transcriptional and chemical measurements of andrimid-treated P. galatheae cultures revealed a 10-fold upregulation of an orphan BGC and, amongst others, a 1.6–2.2-fold upregulation of the gene encoding the core enzyme for biosynthesis of holomycin. Also, addition of andrimid caused an increase, based on UV-Vis peak area, of 4-fold in production of the antibiotic holomycin. Transcriptional measurements of stress response related genes in P. galatheae showed a co-occurrence of increased transcript levels of rpoS (general stress response) and andrimid induced holomycin overproduction, while in trimethoprim treated cultures attenuation of holomycin production coincided with a transcriptional increase of recA (SOS stress response). This study shows that using antimicrobial compounds as activators of secondary metabolism can be a useful strategy in eliciting biosynthetic gene clusters and facilitate natural product discovery. Potentially, such interactions could also have ecological relevant implications.

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

10.1101/2020.05.18.103358 ◽

2020 ◽

Author(s):

Audam Chhun ◽

Despoina Sousoni ◽

Maria del Mar Aguiló-Ferretjans ◽

Lijiang Song ◽

Christophe Corre ◽

...

Keyword(s):

Natural Products ◽

Secondary Metabolites ◽

Antibiotic Production ◽

Antimicrobial Effect ◽

Gene Clusters ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Marine Actinobacteria ◽

Salinispora Tropica ◽

Eukaryotic Phytoplankton

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.

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IMG-ABC: A Knowledge Base To Fuel Discovery of Biosynthetic Gene Clusters and Novel Secondary Metabolites

mBio ◽

10.1128/mbio.00932-15 ◽

2015 ◽

Vol 6 (4) ◽

Cited By ~ 66

Author(s):

Michalis Hadjithomas ◽

I-Min Amy Chen ◽

Ken Chu ◽

Anna Ratner ◽

Krishna Palaniappan ◽

...

Keyword(s):

Secondary Metabolites ◽

Secondary Metabolism ◽

Genomic Data ◽

Gene Clusters ◽

Metagenomic Data ◽

Integrated Analysis ◽

Analysis Tool ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Analysis Tools

ABSTRACTIn the discovery of secondary metabolites, analysis of sequence data is a promising exploration path that remains largely underutilized due to the lack of computational platforms that enable such a systematic approach on a large scale. In this work, we present IMG-ABC (https://img.jgi.doe.gov/abc), an atlas of biosynthetic gene clusters within the Integrated Microbial Genomes (IMG) system, which is aimed at harnessing the power of “big” genomic data for discovering small molecules. IMG-ABC relies on IMG's comprehensive integrated structural and functional genomic data for the analysis of biosynthetic gene clusters (BCs) and associated secondary metabolites (SMs). SMs and BCs serve as the two main classes of objects in IMG-ABC, each with a rich collection of attributes. A unique feature of IMG-ABC is the incorporation of both experimentally validated and computationally predicted BCs in genomes as well as metagenomes, thus identifying BCs in uncultured populations and rare taxa. We demonstrate the strength of IMG-ABC's focused integrated analysis tools in enabling the exploration of microbial secondary metabolism on a global scale, through the discovery of phenazine-producing clusters for the first time inAlphaproteobacteria. IMG-ABC strives to fill the long-existent void of resources for computational exploration of the secondary metabolism universe; its underlying scalable framework enables traversal of uncovered phylogenetic and chemical structure space, serving as a doorway to a new era in the discovery of novel molecules.IMPORTANCEIMG-ABC is the largest publicly available database of predicted and experimental biosynthetic gene clusters and the secondary metabolites they produce. The system also includes powerful search and analysis tools that are integrated with IMG's extensive genomic/metagenomic data and analysis tool kits. As new research on biosynthetic gene clusters and secondary metabolites is published and more genomes are sequenced, IMG-ABC will continue to expand, with the goal of becoming an essential component of any bioinformatic exploration of the secondary metabolism world.

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A Comparative Analysis of Biosynthetic Gene Clusters in Lean and Obese Humans

BioMed Research International ◽

10.1155/2019/6361320 ◽

2019 ◽

Vol 2019 ◽

pp. 1-7 ◽

Cited By ~ 1

Author(s):

Shengqin Wang ◽

Na Li ◽

Nan Li ◽

Huixi Zou ◽

Mingjiang Wu

Keyword(s):

Gut Microbiome ◽

Gene Clusters ◽

Human Adipose Tissue ◽

Taxonomic Diversity ◽

Metagenomic Data ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Intestinal Microbes ◽

Microbe Interactions ◽

Treatment Of Obesity

Obesity is intrinsically linked with the gut microbiome, and studies have identified several obesity-associated microbes. The microbe-microbe interactions can alter the composition of the microbial community and influence host health by producing secondary metabolites (SMs). However, the contribution of these SMs in the prevention and treatment of obesity has been largely ignored. We identified several SM-encoding biosynthetic gene clusters (BGCs) from the metagenomic data of lean and obese individuals and found significant association between some BGCs, including those that produce hitherto unknown SM, and obesity. In addition, the mean abundance of BGCs was positively correlated with obesity, consistent with the lower taxonomic diversity in the gut microbiota of obese individuals. By comparing the BGCs of known SM between obese and nonobese samples, we found that menaquinone produced by Enterobacter cloacae showed the highest correlation with BMI, in agreement with a recent study on human adipose tissue composition. Furthermore, an obesity-related nonribosomal peptide synthetase (NRPS) was negatively associated with Bacteroidetes, indicating that the SMs produced by intestinal microbes in obese individuals can change the microbiome structure. This is the first systemic study of the association between gut microbiome BGCs and obesity and provides new insights into the causes of obesity.

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Competition sensing alters antibiotic production in Streptomyces

10.1101/2020.01.24.918557 ◽

2020 ◽

Cited By ~ 2

Author(s):

Sanne Westhoff ◽

Alexander Kloosterman ◽

Stephan F. A. van Hoesel ◽

Gilles P. van Wezel ◽

Daniel E. Rozen

Keyword(s):

Genetic Relatedness ◽

Cell Damage ◽

Antibiotic Production ◽

Interference Competition ◽

Resource Limitation ◽

Gene Clusters ◽

Regulatory Control ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

The Social

ABSTRACTOne of the most important ways that bacteria compete for resources and space is by producing antibiotics that inhibit competitors. Because antibiotic production is costly, the biosynthetic gene clusters coordinating their synthesis are under strict regulatory control and often require “elicitors” to induce expression, including cues from competing strains. Although these cues are common, they are not produced by all competitors and so the phenotypes causing induction remain unknown. By studying interactions between 24 antibiotic-producing streptomycetes we show that inhibition between competitors is common and occurs more frequently if strains are closely related. Next, we show that antibiotic production is more likely to be induced by cues from strains that are closely related or that share secondary metabolite biosynthetic gene clusters (BGCs). Unexpectedly, antibiotic production is less likely to be induced by competitors that inhibit the growth of a focal strain, indicating that cell damage is not a general cue for induction. In addition to induction, antibiotic production often decreased in the presence of a competitor, although this response was not associated with genetic relatedness or overlap in BGCs. Finally, we show that resource limitation increases the chance that antibiotic production declines during competion. Our results reveal the importance of social cues and resource availability in the dynamics of interference competition in streptomycetes.SIGNIFICANCE STATEMENTBacteria secrete antibiotics to inhibit their competitors, but the presence of competitors can determine whether these toxins are produced. Here, we study the role of the competitive and resource environment on antibiotic production in Streptomyces, bacteria renowned for their production of antibiotics. We show that Streptomyces are more likely to produce antibiotics when grown with closely related competitors or that share biosynthetic pathways for secondary metabolites, but not when they are threatened by competitor’s toxins, in contrast to predictions of the competition sensing hypothesis. Streptomyces also often reduce their output of antibiotics when grown with competitors, especially under nutrient limitation. Our findings highlight that interactions between the social and resource environments strongly regulate antibiotic production in these medicinally important bacteria.

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Microbiological and molecular insights on rare Actinobacteria harboring bioactive prospective

Bulletin of the National Research Centre ◽

10.1186/s42269-019-0266-8 ◽

2020 ◽

Vol 44 (1) ◽

Author(s):

Dina H. Amin ◽

Nagwa A. Abdallah ◽

Assem Abolmaaty ◽

Sahar Tolba ◽

Elizabeth M. H. Wellington

Keyword(s):

Bioinformatics Analysis ◽

Genetic Manipulation ◽

Antibiotic Production ◽

Gene Clusters ◽

Bioactive Molecules ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Pcr Screening ◽

Molecular Approaches ◽

Shed Light

Abstract Background Actinobacteria is as a group of advanced filamentous bacteria. Rare Actinobacteria are of special interest as they are rarely isolated from the environments. They are a major source of important bioactive compounds. Determining the proper strategy for the identification of Actinobacteria harboring biosynthetic gene clusters and producing bioactive molecules is a challenging platform. Methodology In this review, we discuss a consequence of microbiological and molecular methods for the identification of rare Actinobacteria. In addition to that, we shed light on rare Actinobacteria’s significance in antibiotic production. We also clarified molecular approaches for the manipulation of novel biosynthetic gene clusters via PCR screening, fosmid libraries, and Illumina whole-genome sequencing in combination with bioinformatics analysis. Conclusion Perceptions of the conventional and molecular identification of Actinobacteria were conducted. This will open the door for the genetic manipulation of novel antibiotic gene clusters in heterologous hosts. Also, these conclusions will lead to constructing new bioactive molecules via genetically engineering biosynthetic pathways.

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Competition Sensing Changes Antibiotic Production in Streptomyces

mBio ◽

10.1128/mbio.02729-20 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Sanne Westhoff ◽

Alexander M. Kloosterman ◽

Stephan F. A. van Hoesel ◽

Gilles P. van Wezel ◽

Daniel E. Rozen

Keyword(s):

Genetic Relatedness ◽

Cell Damage ◽

Antibiotic Production ◽

Interference Competition ◽

Resource Limitation ◽

Gene Clusters ◽

Regulatory Control ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

The Social

ABSTRACT One of the most important ways that bacteria compete for resources and space is by producing antibiotics that inhibit competitors. Because antibiotic production is costly, the biosynthetic gene clusters coordinating their synthesis are under strict regulatory control and often require “elicitors” to induce expression, including cues from competing strains. Although these cues are common, they are not produced by all competitors, and so the phenotypes causing induction remain unknown. By studying interactions between 24 antibiotic-producing strains of streptomycetes, we show that strains commonly inhibit each other’s growth and that this occurs more frequently if strains are closely related. Next, we show that antibiotic production is more likely to be induced by cues from strains that are closely related or that share secondary metabolite biosynthetic gene clusters (BGCs). Unexpectedly, antibiotic production is less likely to be induced by competitors that inhibit the growth of a focal strain, indicating that cell damage is not a general cue for induction. In addition to induction, antibiotic production often decreases in the presence of a competitor, although this response was not associated with genetic relatedness or overlap in BGCs. Finally, we show that resource limitation increases the chance that antibiotic production declines during competition. Our results reveal the importance of social cues and resource availability in the dynamics of interference competition in streptomycetes. IMPORTANCE Bacteria secrete antibiotics to inhibit their competitors, but the presence of competitors can determine whether these toxins are produced. Here, we study the role of the competitive and resource environment on antibiotic production in Streptomyces, bacteria renowned for their production of antibiotics. We show that Streptomyces cells are more likely to produce antibiotics when grown with competitors that are closely related or that share biosynthetic pathways for secondary metabolites, but not when they are threatened by competitor’s toxins, in contrast to predictions of the competition sensing hypothesis. Streptomyces cells also often reduce their output of antibiotics when grown with competitors, especially under nutrient limitation. Our findings highlight that interactions between the social and resource environments strongly regulate antibiotic production in these medicinally important bacteria.

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Synergistic activity of cosecreted natural products from amoebae-associated bacteria

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1721790115 ◽

2018 ◽

Vol 115 (15) ◽

pp. 3758-3763 ◽

Cited By ~ 27

Author(s):

Johannes Arp ◽

Sebastian Götze ◽

Ruchira Mukherji ◽

Derek J. Mattern ◽

María García-Altares ◽

...

Keyword(s):

Natural Products ◽

Polyketide Synthase ◽

Bacterial Genome ◽

Gene Clusters ◽

Homoserine Lactone ◽

Microbial Interactions ◽

Signal Molecules ◽

Synergistic Activity ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters

Investigating microbial interactions from an ecological perspective is a particularly fruitful approach to unveil both new chemistry and bioactivity. Microbial predator–prey interactions in particular rely on natural products as signal or defense molecules. In this context, we identified a grazing-resistant Pseudomonas strain, isolated from the bacterivorous amoeba Dictyostelium discoideum. Genome analysis of this bacterium revealed the presence of two biosynthetic gene clusters that were found adjacent to each other on a contiguous stretch of the bacterial genome. Although one cluster codes for the polyketide synthase producing the known antibiotic mupirocin, the other cluster encodes a nonribosomal peptide synthetase leading to the unreported cyclic lipopeptide jessenipeptin. We describe its complete structure elucidation, as well as its synergistic activity against methicillin-resistant Staphylococcus aureus, when in combination with mupirocin. Both biosynthetic gene clusters are regulated by quorum-sensing systems, with 3-oxo-decanoyl homoserine lactone (3-oxo-C10-AHL) and hexanoyl homoserine lactone (C6-AHL) being the respective signal molecules. This study highlights the regulation, richness, and complex interplay of bacterial natural products that emerge in the context of microbial competition.

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TaxiBGC: a Taxonomy-guided Approach for the Identification of Experimentally Verified Microbial Biosynthetic Gene Clusters in Shotgun Metagenomic Data

10.1101/2021.07.30.454505 ◽

2021 ◽

Author(s):

Utpal Bakshi ◽

Vinod K Gupta ◽

Aileen R Lee ◽

John M Davis ◽

Sriram Chandrasekaran ◽

...

Keyword(s):

Large Scale ◽

Human Microbiome ◽

Gene Clusters ◽

Human Microbiome Project ◽

Metagenomic Data ◽

Biosynthetic Gene ◽

Case Control Studies ◽

Biosynthetic Gene Clusters ◽

Host Interactions ◽

Microbiome Data

Biosynthetic gene clusters (BGCs) in microbial genomes encode for the production of bioactive secondary metabolites (SMs). Given the well-recognized importance of SMs in microbe-microbe and microbe-host interactions, the large-scale identification of BGCs from microbial metagenomes could offer novel functional insights into complex chemical ecology. Despite recent progress, currently available tools for predicting BGCs from shotgun metagenomes have several limitations, including the need for computationally demanding read-assembly and prediction of a narrow breadth of BGC classes. To overcome these limitations, we developed TaxiBGC (Taxonomy-guided Identification of Biosynthetic Gene Clusters), a computational pipeline for identifying experimentally verified BGCs in shotgun metagenomes by first pinpointing the microbial species likely to produce them. We show that our species-centric approach was able to identify BGCs in simulated metagenomes more accurately than by solely detecting BGC genes. By applying TaxiBGC on 5,423 metagenomes from the Human Microbiome Project and various case-control studies, we identified distinct BGC signatures of major human body sites and candidate stool-borne biomarkers for multiple diseases, including inflammatory bowel disease, colorectal cancer, and psychiatric disorders. In all, TaxiBGC demonstrates a significant advantage over existing techniques for systematically characterizing BGCs and inferring their SMs from microbiome data.

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Unique physiological and genetic features of ofloxacin-resistant Streptomyces mutants

Applied and Environmental Microbiology ◽

10.1128/aem.02327-21 ◽

2021 ◽

Author(s):

Kanata Hoshino ◽

Ryoko Hamauzu ◽

Hiroyuki Nakagawa ◽

Shinya Kodani ◽

Takeshi Hosaka

Keyword(s):

Drug Resistance ◽

Secondary Metabolites ◽

Secondary Metabolite ◽

Antimicrobial Agents ◽

Gene Clusters ◽

Resistant Bacteria ◽

Biosynthetic Gene ◽

Biosynthetic Gene Clusters ◽

Resistance Selection ◽

Resistant Mutants

New antimicrobial agents are urgently needed to combat the emergence and spread of multidrug-resistant bacteria. Activating the cryptic biosynthetic gene clusters for actinomycete secondary metabolites can provide essential clues for research into new antimicrobial agents. An effective method for this purpose is based on drug resistance selection. This report describes interesting results for drug resistance selection using antibiotics that target DNA replication can effectively potentiate secondary metabolite production by actinomycetes. Ofloxacin-resistant mutants were isolated from five different streptomycetes. Ofloxacin is an antibiotic that binds to DNA complexes and type II topoisomerase, causing double-stranded breaks in bacterial chromosomes. Physiological and genetic characterization of the mutants revealed that the development of ofloxacin resistance in streptomycetes leads to the emergence of various types of secondary metabolite-overproducing strains. In Streptomyces coelicolor A3(2), ofloxacin-resistant mutants that overproduced actinorhodin, undecylprodigiosin, or carotenoid were identified. Also, an ofloxacin-resistant mutant that overproduces methylenomycin A, whose biosynthetic gene cluster is located on the endogenous plasmid, SCP1, was isolated. These observations indicate that ofloxacin resistance might activate biosynthetic genes on both chromosomes and on endogenous plasmids. We also identified the mutations that are probably involved in the phenotype of ofloxacin resistance and secondary metabolite overproduction in S. coelicolor A3(2). Furthermore, we observed an interesting phenomenon in which several ofloxacin-resistant mutants overproduced antibiotics in the presence of ofloxacin. Based on these results, we present the unique physiological and genetic characteristics of ofloxacin-resistant Streptomyces mutants and discuss the importance and potential development of the new findings. IMPORTANCE The abuse or overuse of antibacterial agents for therapy and animal husbandry has caused an increased population of antimicrobial-resistant bacteria in the environment. Consequently, there are now fewer effective antimicrobials available. Due to the depleted antibiotic pipeline, pandemic outbreaks caused by antimicrobial-resistant bacteria are deeply concerned, and the development of new antibiotics is now an urgent issue. Promising sources of antimicrobial agents include cryptic biosynthetic gene clusters for secondary metabolites in streptomycetes and rare actinomycetes. This study’s significance is an unprecedented activation method to accelerate drug discovery research on a global scale. The technique developed in this study could allow for simultaneous drug discovery in different countries, maximizing the world’s microbial resources.

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