scholarly journals Novel mechanism of metabolic co-regulation coordinates the biosynthesis of secondary metabolites in Pseudomonas protegens

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Qing Yan ◽  
Benjamin Philmus ◽  
Jeff H Chang ◽  
Joyce E Loper
Keyword(s):  
Secondary Metabolites ◽  
Gene Cluster ◽  
Erwinia Amylovora ◽  
Microbial Interactions ◽  
Pathogenic Bacterium ◽  
Soil Bacterium ◽  
Biosynthetic Pathways ◽  
Plant Pathogenic Bacterium ◽  
Biosynthetic Genes ◽  
Antimicrobial Metabolites

Metabolic co-regulation between biosynthetic pathways for secondary metabolites is common in microbes and can play an important role in microbial interactions. Here, we describe a novel mechanism of metabolic co-regulation in which an intermediate in one pathway is converted into signals that activate a second pathway. Our study focused on the co-regulation of 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin, two antimicrobial metabolites produced by the soil bacterium Pseudomonas protegens. We show that an intermediate in DAPG biosynthesis, phloroglucinol, is transformed by a halogenase encoded in the pyoluteorin gene cluster into mono- and di-chlorinated phloroglucinols. The chlorinated phloroglucinols function as intra- and inter-cellular signals that induce the expression of pyoluteorin biosynthetic genes, pyoluteorin production, and pyoluteorin-mediated inhibition of the plant-pathogenic bacterium Erwinia amylovora. This metabolic co-regulation provides a strategy for P. protegens to optimize the deployment of secondary metabolites with distinct roles in cooperative and competitive microbial interactions.

scholarly journals Chromosomally Encodedhok-sokToxin-Antitoxin System in the Fire Blight PathogenErwinia amylovora: Identification and Functional Characterization

2019 ◽  
Vol 85 (15) ◽  
Author(s):  
Jingyu Peng ◽  
Lindsay R. Triplett ◽  
Jeffrey K. Schachterle ◽  
George W. Sundin
Keyword(s):  
Noncoding Rna ◽  
Pathogenic Bacteria ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Functional Characterization ◽  
Pathogenic Bacterium ◽  
Type I ◽  
Plant Pathogenic Bacterium ◽  
Content Type ◽  
Protein Toxin

ABSTRACTToxin-antitoxin (TA) systems are genetic elements composed of a protein toxin and a counteracting antitoxin that is either a noncoding RNA or protein. In type I TA systems, the antitoxin is a noncoding small RNA (sRNA) that base pairs with the cognate toxin mRNA interfering with its translation. Although type I TA systems have been extensively studied inEscherichia coliand a few human or animal bacterial pathogens, they have not been characterized in plant-pathogenic bacteria. In this study, we characterized a chromosomal locus in the plant pathogenErwinia amylovoraEa1189 that is homologous to thehok-soktype I TA system previously identified in theEnterobacteriaceae-restricted plasmid R1. Phylogenetic analysis indicated that the chromosomal location of thehok-soklocus is, thus far, unique toE. amylovora. We demonstrated that ectopic overexpression ofhokis highly toxic toE. amylovoraand that the sRNAsokreversed the toxicity ofhokthroughmok, a reading frame presumably translationally coupled withhok. We also identified the region that is essential for maintenance of the main toxicity of Hok. Through ahok-sokdeletion mutant (Ea1189Δhok-sok), we determined the contribution of thehok-soklocus to cellular growth, micromorphology, and catalase activity. Combined, our findings indicate that thehok-sokTA system, besides being potentially self-toxic, provides fitness advantages toE. amylovora.IMPORTANCEBacterial toxin-antitoxin systems have received great attention because of their potential as targets for antimicrobial development and as tools for biotechnology.Erwinia amylovora, the causal agent of fire blight disease on pome fruit trees, is a major plant-pathogenic bacterium. In this study, we identified and functionally characterized a unique chromosomally encodedhok-soktoxin-antitoxin system inE. amylovorathat resembles the plasmid-encoded copies of this system in otherEnterobacteriaceae. This study of a type I toxin-antitoxin system in a plant-pathogenic bacterium provides the basis to further understand the involvement of toxin-antitoxin systems during infection by a plant-pathogenic bacterium. The new linkage between thehok-soktoxin-antitoxin system and the catalase-mediated oxidative stress response leads to additional considerations of targeting this system for antimicrobial development.

scholarly journals Conserved Responses in a War of Small Molecules between a Plant-Pathogenic Bacterium and Fungi

mBio ◽  
2018 ◽  
Vol 9 (3) ◽  
Author(s):  
Joseph E. Spraker ◽  
Philipp Wiemann ◽  
Joshua A. Baccile ◽  
Nandhitha Venkatesh ◽  
Julia Schumacher ◽  
...  
Keyword(s):  
Botrytis Cinerea ◽  
Gene Cluster ◽  
Ralstonia Solanacearum ◽  
Pathogenic Fungi ◽  
Gene Clusters ◽  
Pathogenic Bacterium ◽  
Fusarium Fujikuroi ◽  
Plant Pathogenic Fungi ◽  
Plant Pathogenic Bacterium ◽  
Content Type

ABSTRACTSmall-molecule signaling is one major mode of communication within the polymicrobial consortium of soil and rhizosphere. While microbial secondary metabolite (SM) production and responses of individual species have been studied extensively, little is known about potentially conserved roles of SM signals in multilayered symbiotic or antagonistic relationships. Here, we characterize the SM-mediated interaction between the plant-pathogenic bacteriumRalstonia solanacearumand the two plant-pathogenic fungiFusarium fujikuroiandBotrytis cinerea. We show that cellular differentiation and SM biosynthesis inF. fujikuroiare induced by the bacterially produced lipopeptide ralsolamycin (synonym ralstonin A). In particular, fungal bikaverin production is induced and preferentially accumulates in fungal survival spores (chlamydospores) only when exposed to supernatants of ralsolamycin-producing strains ofR. solanacearum. Although inactivation of bikaverin biosynthesis moderately increases chlamydospore invasion byR. solanacearum, we show that other metabolites such as beauvericin are also induced by ralsolamycin and contribute to suppression ofR. solanacearumgrowthin vitro. Based on our findings that bikaverin antagonizesR. solanacearumand that ralsolamycin induces bikaverin biosynthesis inF. fujikuroi, we asked whether other bikaverin-producing fungi show similar responses to ralsolamycin. Examining a strain ofB. cinereathat horizontally acquired the bikaverin gene cluster fromFusarium, we found that ralsolamycin induced bikaverin biosynthesis in this fungus. Our results suggest that conservation of microbial SM responses across distantly related fungi may arise from horizontal transfer of protective gene clusters that are activated by conserved regulatory cues, e.g., a bacterial lipopeptide, providing consistent fitness advantages in dynamic polymicrobial networks.IMPORTANCEBacteria and fungi are ubiquitous neighbors in many environments, including the rhizosphere. Many of these organisms are notorious as economically devastating plant pathogens, but little is known about how they communicate chemically with each other. Here, we uncover a conserved antagonistic communication between the widespread bacterial wilt pathogenRalstonia solanacearumand plant-pathogenic fungi from disparate genera,FusariumandBotrytis. Exposure ofFusarium fujikuroito the bacterial lipopeptide ralsolamycin resulted in production of the antibacterial metabolite bikaverin specifically in fungal tissues invaded byRalstonia. Remarkably, ralsolamycin induction of bikaverin was conserved in aBotrytis cinereaisolate carrying a horizontally transferred bikaverin gene cluster. These results indicate that horizontally transferred gene clusters may carry regulatory prompts that contribute to conserved fitness functions in polymicrobial environments.

scholarly journals Meroterpenoids: A Comprehensive Update Insight on Structural Diversity and Biology

Biomolecules ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 957
Author(s):  
Mamona Nazir ◽  
Muhammad Saleem ◽  
Muhammad Imran Tousif ◽  
Muhammad Aijaz Anwar ◽  
Frank Surup ◽  
...  
Keyword(s):  
Amino Acids ◽  
Secondary Metabolites ◽  
Biological Effects ◽  
Structural Diversity ◽  
Chemical Diversity ◽  
Biosynthetic Pathways ◽  
Natural Sources ◽  
Hybrid Compounds ◽  
Anti Inflammatory

Meroterpenoids are secondary metabolites formed due to mixed biosynthetic pathways which are produced in part from a terpenoid co-substrate. These mixed biosynthetically hybrid compounds are widely produced by bacteria, algae, plants, and animals. Notably amazing chemical diversity is generated among meroterpenoids via a combination of terpenoid scaffolds with polyketides, alkaloids, phenols, and amino acids. This review deals with the isolation, chemical diversity, and biological effects of 452 new meroterpenoids reported from natural sources from January 2016 to December 2020. Most of the meroterpenoids possess antimicrobial, cytotoxic, antioxidant, anti-inflammatory, antiviral, enzyme inhibitory, and immunosupressive effects.

scholarly journals Refactoring the formicamycin biosynthetic gene cluster to make high-level producing strains and new molecules

2020 ◽  
Author(s):  
Rebecca Devine ◽  
Hannah McDonald ◽  
Zhiwei Qin ◽  
Corinne Arnold ◽  
Katie Noble ◽  
...  
Keyword(s):  
Gene Cluster ◽  
Large Scale ◽  
Liquid Culture ◽  
Gene Clusters ◽  
Biosynthetic Gene Cluster ◽  
Resistant Bacteria ◽  
Drug Resistant ◽  
Biosynthetic Gene ◽  
Biosynthetic Genes

AbstractThe formicamycins are promising antibiotics with potent activity against Gram-positive pathogens including VRE and MRSA and display a high barrier to selection of resistant isolates. They were first identified in Streptomyces formicae KY5, which produces the formicamycins at low levels on solid agar but not in liquid culture, thus hindering further investigation of these promising antibacterial compounds. We hypothesised that by understanding the organisation and regulation of the for biosynthetic gene cluster, we could rationally refactor the cluster to increase production levels. Here we report that the for biosynthetic gene cluster consists of 24 genes expressed on nine transcripts. Seven of these transcripts, including those containing all the major biosynthetic genes, are repressed by the MarR-regulator ForJ which also controls the expression of the ForGF two-component system that initiates biosynthesis. A third cluster-situated regulator, ForZ, autoregulates and controls production of the putative MFS transporter ForAA. Consistent with these findings, deletion of forJ increased formicamycin biosynthesis 5-fold, while over-expression of forGF in the ΔforJ background increased production 10-fold compared to the wild-type. De-repression by deleting forJ also switched on biosynthesis in liquid-culture and induced the production of two novel formicamycin congeners. By combining mutations in regulatory and biosynthetic genes, six new biosynthetic precursors with antibacterial activity were also isolated. This work demonstrates the power of synthetic biology for the rational redesign of antibiotic biosynthetic gene clusters both to engineer strains suitable for fermentation in large scale bioreactors and to generate new molecules.ImportanceAntimicrobial resistance is a growing threat as existing antibiotics become increasingly ineffective against drug resistant pathogens. Here we determine the transcriptional organisation and regulation of the gene cluster encoding biosynthesis of the formicamycins, promising new antibiotics with activity against drug resistant bacteria. By exploiting this knowledge, we construct stable mutant strains which over-produce these molecules in both liquid and solid culture whilst also making some new compound variants. This will facilitate large scale purification of these molecules for further study including in vivo experiments and the elucidation of their mechanism of action. Our work demonstrates that understanding the regulation of natural product biosynthetic pathways can enable rational improvement of the producing strains.

scholarly journals The fungal gene cluster for biosynthesis of the antibacterial agent viriditoxin

2019 ◽  
Author(s):  
Andrew S. Urquhart ◽  
Jinyu Hu ◽  
Yit-Heng Chooi ◽  
Alexander Idnurm
Keyword(s):  
Secondary Metabolites ◽  
Gene Cluster ◽  
Gene Disruption ◽  
Biosynthetic Pathway ◽  
Fluorescent Protein ◽  
Model Species ◽  
Paecilomyces Variotii ◽  
Bioinformatic Approaches ◽  
Green Fluorescent ◽  
Fungal Gene

AbstractBackgroundViriditoxin is one of the ‘classical’ secondary metabolites produced by fungi and that has antibacterial and other activities; however, the mechanism of its biosynthesis has remained unknown.ResultsHere, a gene cluster responsible for its synthesis was identified, using bioinformatic approaches from two species that produce viriditoxin and then through gene disruption and metabolite profiling. All eight genes in the cluster inPaecilomyces variotiiwere mutated, revealing their roles in the synthesis of this molecule and establishing its biosynthetic pathway which includes an interesting Baeyer-Villiger monooxygenase catalyzed reaction. Additionally, a candidate catalytically-inactive hydrolase was identified as being required for the stereoselective biosynthesis of (M)-viriditoxin. The localization of two proteins were assessed by fusing these proteins to green fluorescent protein, revealing that at least two intracellular structures are involved in the compartmentalization of the synthesis steps of this metabolite.ConclusionsThe full pathway for synthesis of viriditoxin was established by a combination of genomics, bioinformatics, gene disruption and chemical analysis processes. Hence, this work reveals the basis for the synthesis of an understudied class of fungal secondary metabolites and provides a new model species for understanding the synthesis of biaryl compounds with a chiral axis.

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