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PloS One 2020Pseudomonas chlororaphis strain PA23 is a biocontrol agent capable of protecting canola from stem rot disease caused by the fungal pathogen Sclerotinia sclerotiorum....
Pseudomonas chlororaphis strain PA23 is a biocontrol agent capable of protecting canola from stem rot disease caused by the fungal pathogen Sclerotinia sclerotiorum. PA23 produces several inhibitory compounds that are under control of a complex regulatory network. Included in this cascade is the PhzRI quorum sensing (QS) system, which plays an essential role in PA23 biocontrol, as well as CsaRI and AurRI, which have not yet been characterized in PA23. The focus of the current study was to employ RNA sequencing to explore the spectrum of PA23 genes under QS control. In this work, we investigated genes under the control of the main QS transcriptional regulator, PhzR, as well as those differentially expressed in an AHL-deficient strain, PA23-6863, which constitutively expresses an AiiA lactonase, rendering the strain QS defective. Transcriptomic profiling revealed 545 differentially expressed genes (365 downregulated; 180 upregulated) in the phzR mutant and 534 genes (382 downregulated; 152 upregulated) in the AHL-deficient PA23-6863. In both strains, decreased expression of phenazine, pyrrolnitrin, and exoprotease biosynthetic genes was observed. We have previously reported that QS activates expression of these genes and their encoded products. In addition, elevated siderophore and decreased chitinase gene expression was observed in the QS-deficient stains, which was confirmed by phenotypic analysis. Inspection of the promoter regions revealed the presence of "phz-box" sequences in only 58 of the 807 differentially expressed genes, suggesting that much of the QS regulon is indirectly regulated. Consistent with this notion, 41 transcriptional regulators displayed altered expression in one or both of the QS-deficient strains. Collectively, our findings indicate that QS governs expression of approximately 13% of the PA23 genome affecting diverse functions ranging from secondary metabolite production to general metabolism.
Topics: Bacterial Proteins; Carboxylic Ester Hydrolases; Cell Movement; Chitinases; Gene Expression Regulation, Bacterial; Mutant Proteins; Pest Control, Biological; Pseudomonas chlororaphis; Quorum Sensing; RNA-Seq; Regulon; Siderophores; Trans-Activators; Transcriptome
PubMed: 32109244
DOI: 10.1371/journal.pone.0226232 -
Phytopathology May 2020A four-gene operon () from Pf-5 encoding the biosynthesis of the antibiotic pyrronitrin was introduced into (formerly ) 2-79, an aggressive root colonizer of both...
A four-gene operon () from Pf-5 encoding the biosynthesis of the antibiotic pyrronitrin was introduced into (formerly ) 2-79, an aggressive root colonizer of both dryland and irrigated wheat roots that naturally produces the antibiotic phenazine-1-carboxylic acid and suppresses both take-all and Rhizoctonia root rot of wheat. Recombinant strains ZHW15 and ZHW25 produced both antibiotics and maintained population sizes in the rhizosphere of wheat that were comparable to those of strain 2-79. The recombinant strains inhibited in vitro the wheat pathogens anastomosis group 8 (AG-8) and AG-2-1, var. , , , and significantly more than did strain 2-79. Both the wild-type and recombinant strains were equally inhibitory of . When applied as a seed treatment, the recombinant strains suppressed take-all, Rhizoctonia root rot of wheat, and Rhizoctonia root and stem rot of canola significantly better than did wild-type strain 2-79.
Topics: Plant Diseases; Pseudomonas; Pseudomonas fluorescens; Pyrrolnitrin
PubMed: 32065038
DOI: 10.1094/PHYTO-09-19-0367-R -
Journal of Medical Microbiology Mar 2020isolates have been studied intensively for their beneficial traits. species function as probiotics in plants and fish, offering plants protection against microbes,... (Review)
Review
isolates have been studied intensively for their beneficial traits. species function as probiotics in plants and fish, offering plants protection against microbes, nematodes and insects. In this review, we discuss the classification of isolates within four subspecies; the shared traits include the production of coloured antimicrobial phenazines, high sequence identity between housekeeping genes and similar cellular fatty acid composition. The direct antimicrobial, insecticidal and nematocidal effects of isolates are correlated with known metabolites. Other metabolites prime the plants for stress tolerance and participate in microbial cell signalling events and biofilm formation among other things. Formulations of isolates and their metabolites are currently being commercialized for agricultural use.
Topics: Acyl-Butyrolactones; Agriculture; Anti-Infective Agents; Antinematodal Agents; Biofilms; Hydrogen Cyanide; Insecticides; Phenazines; Phenotype; Plants; Probiotics; Pseudomonas chlororaphis; Pyrrolnitrin; Resorcinols; Siderophores; Volatile Organic Compounds
PubMed: 32043956
DOI: 10.1099/jmm.0.001157 -
Organic Letters Feb 2020Pyonitrins A-D are recently isolated natural products from the insect-associated strain, which were isolated from complex fractions that exhibited antifungal activity...
Pyonitrins A-D are recently isolated natural products from the insect-associated strain, which were isolated from complex fractions that exhibited antifungal activity via an murine candidiasis assay. Genomic studies of suggested that pyonitrins A-D are formed via a spontaneous nonenzymatic reaction between biosynthetic intermediates of two well-known natural products pyochelin and pyrrolnitrin. Herein we have accomplished the first biomimetic total synthesis of pyonitrins A-D in three steps and studied the nonenzymatic formation of the pyonitrins using N NMR spectroscopy.
Topics: Antifungal Agents; Candida albicans; Magnetic Resonance Spectroscopy; Microbial Sensitivity Tests; Molecular Structure; Pseudomonas; Stereoisomerism; Thiazoles
PubMed: 32017580
DOI: 10.1021/acs.orglett.0c00098 -
Journal of the American Chemical Society Oct 2019Bacterial symbionts frequently provide chemical defenses for their hosts, and such systems can provide discovery pathways to new antifungals and structurally intriguing...
Bacterial symbionts frequently provide chemical defenses for their hosts, and such systems can provide discovery pathways to new antifungals and structurally intriguing metabolites. This report describes a small family of naturally occurring small molecules with chimeric structures and a mixed biosynthesis that features an unexpected but key nonenzymatic step. An insect-associated strain's activity in an murine candidiasis assay led to the discovery of a family of highly hydrogen-deficient metabolites. Bioactivity- and mass-guided fractionation led to the pyonitrins, highly complex aromatic metabolites in which 10 of the 20 carbons are quaternary, and 7 of them are contiguous. The genome revealed that the production of the pyonitrins is the result of a spontaneous reaction between biosynthetic intermediates of two well-studied metabolites, pyochelin and pyrrolnitrin. The combined discovery of the pyonitrins and identification of the responsible biosynthetic gene clusters revealed an unexpected biosynthetic route that would have prevented the discovery of these metabolites by bioinformatic analysis alone.
Topics: Animals; Antifungal Agents; Bacterial Proteins; Biological Products; Biosynthetic Pathways; Candida albicans; Candidiasis; Chromatography, High Pressure Liquid; Drug Evaluation, Preclinical; Magnetic Resonance Spectroscopy; Mice; Molecular Structure; Phenols; Pseudomonas; Pyrrolnitrin; Thiazoles
PubMed: 31600443
DOI: 10.1021/jacs.9b09739 -
Applied Biochemistry and Biotechnology Mar 2020The extensive use of chemical fungicide in the health and agriculture sectors has increased environmental concerns and promoted an extensive search for alternative...
Pyrrolnitrin from Rhizospheric Serratia marcescens NCIM 5696: Optimization of Process Parameters Using Statistical Tools and Seed-Applied Bioprotectants for Vigna radiata (L.) Against Fusarium oxysporum MTCC 9913.
The extensive use of chemical fungicide in the health and agriculture sectors has increased environmental concerns and promoted an extensive search for alternative bioactives from the microbial system. In the present study, two rhizospheric strains of Serratia spp. (TO-2 and TW-3) have been shown to secrete pyrrolnitrin (PRN) in the range of 11.35 to 35.97 μg ml using MSG and MSD medium after 72 h under static and shake conditions, respectively, but thereafter marginally declined in 96 to 240 h. Alternative one variable assortment at a time (OVAT) for PRN secretion by TW-3 yielded 59.27 μg ml using (gl) glycerol (20), monosodium glutamate (14), KHPO (14), NHCl (3), NaHPO (4), and MgSO (0.3) at pH 7, 120 rpm within 72 h. Further, the Placket-Burman Design (PBD) identified KHPO, glycerol, pH, and monosodium glutamate as significant variables and optimized by centered composite design. Accordingly, 3% glycerol, 1.72% KHPO, 1.1% monosodium glutamate, 0.4% NaHPO, 0.03% MgSO, 0.05% FeSO, and 0.01% ZnSO were found to enhance the yield of PRN to 96.54 μg ml by TW-3 in 72 h, 120 rpm. Thus, the statistical tool employed in the present study showed a threefold hike in PRN secretion over the OVAT approach, thereby indicating the scope for more PRN production from rhizobacteria. Further, seed application of low PRN (30 μg ml) concentration in treatments I and II showed > 90% germination in the initial seed germination and pot assay with the Fusarium oxysporum challenge compared to the control. Also, various growth parameters calculated during 11 days of experiment were significantly increased compared to the negative control (seed + fungus) in both treatments. Thus, the application of PRN at a low concentration to seeds of Vigna radiata (L.) offered protection against the phytopathogenic F. oxysporum MTCC 9913 challenge, suggesting biocontrol activity potential for use in agriculture soils particularly salt-affected soil.
Topics: Fungicides, Industrial; Fusarium; Pyrrolnitrin; Rhizosphere; Seeds; Serratia marcescens; Soil; Soil Microbiology; Vigna
PubMed: 31493159
DOI: 10.1007/s12010-019-03123-w -
Biomolecules Sep 2019Pyrrolnitrin (PRN) is a microbial pyrrole halometabolite of immense antimicrobial significance for agricultural, pharmaceutical and industrial implications. The compound... (Review)
Review
Pyrrolnitrin (PRN) is a microbial pyrrole halometabolite of immense antimicrobial significance for agricultural, pharmaceutical and industrial implications. The compound and its derivatives have been isolated from rhizospheric fluorescent or non-fluorescent pseudomonads, and . They are known to confer biological control against a wide range of phytopathogenic fungi, and thus offer strong plant protection prospects against soil and seed-borne phytopathogenic diseases. Although chemical synthesis of PRN has been obtained using different steps, microbial production is still the most useful option for producing this metabolite. In many of the plant-associated isolates of and , production of PRN is dependent on the quorum-sensing regulation that usually involves N-acylhomoserine lactone (AHL) autoinducer signals. When applied on the organisms as antimicrobial agent, the molecule impedes synthesis of key biomolecules (DNA, RNA and protein), uncouples with oxidative phosphorylation, inhibits mitotic division and hampers several biological mechanisms. With its potential broad-spectrum activities, low phototoxicity, non-toxic nature and specificity for impacts on non-target organisms, the metabolite has emerged as a lead molecule of industrial importance, which has led to developing cost-effective methods for the biosynthesis of PRN using microbial fermentation. Quantum of work narrating focused research efforts in the emergence of this potential microbial metabolite is summarized here to present a consolidated, sequential and updated insight into the chemistry, biology and applicability of this natural molecule.
Topics: Antifungal Agents; Burkholderia; Fermentation; Fungi; Microbial Sensitivity Tests; Pseudomonas; Pyrrolnitrin; Serratia
PubMed: 31484394
DOI: 10.3390/biom9090443 -
The Plant Pathology Journal Aug 2019In our previous study, pyrrolnitrin produced in G05 plays more critical role in suppression of mycelial growth of some fungal pathogens that cause plant diseases in...
In our previous study, pyrrolnitrin produced in G05 plays more critical role in suppression of mycelial growth of some fungal pathogens that cause plant diseases in agriculture. Although some regulators for pyrrolnitrin biosynthesis were identified, the pyrrolnitrin regulation pathway was not fully constructed. During our screening novel regulator candidates, we obtained a white conjugant G05W02 while transposon mutagenesis was carried out between a fusion mutant G05ΔΔ:: and S17-1 (pUT/mini-Tn5Kan). By cloning and sequencing of the transposon-flanking DNA fragment, we found that a gene in the conjugant G05W02 was disrupted with mini-Tn5Kan. In one other previous study on , however, it was reported that the deletion of the caused increased production of pyrrolnitrin and other antifungal metabolites. To confirm its regulatory function, we constructed the -knockout mutant G05Δ and G05ΔΔ::Δ. By quantifying β-galactosidase activities, we found that deletion of the decreased the operon expression dramatically. Meanwhile, by quantifying pyrrolnitrin production in the mutant G05Δ, we found that deficiency of the Vfr caused decreased pyrrolnitrin production. However, production of phenazine-1-carboxylic acid was same to that in the wild-type strain G05. Taken together, Vfr is required for pyrrolnitrin but not for phenazine-1-carboxylic acid biosynthesis in G05.
PubMed: 31481858
DOI: 10.5423/PPJ.OA.01.2019.0011