scholarly journals Deleterious Impact of a Virulent Bacteriophage on Survival and Biocontrol Activity of Pseudomonas fluorescens Strain CHA0 in Natural Soil

2002 ◽  
Vol 15 (6) ◽  
pp. 567-576 ◽  
Author(s):  
Christoph Keel ◽  
Zöhre Ucurum ◽  
Patrick Michaux ◽  
Marc Adrian ◽  
Dieter Haas
Keyword(s):  
Pseudomonas Fluorescens ◽  
Population Size ◽  
Abiotic Factors ◽  
Pythium Ultimum ◽  
Plant Diseases ◽  
Natural Soil ◽  
Lytic Bacteriophage ◽  
Resistant Variant ◽  
A Genome ◽  
Biocontrol Activity

Many biotic and abiotic factors affect the persistence and activity of beneficial pseudomonads introduced into soil to suppress plant diseases. One such factor may be the presence of virulent bacteriophages that decimate the population of the introduced bacteria, thereby reducing their beneficial effect. We have isolated a lytic bacteriophage (ΦGP100) that specifically infects the biocontrol bacterium Pseudomonas fluorescens CHA0 and some closely related Pseudomonas strains. ΦGP100 was found to be a doublestranded-DNA phage with an icosahedral head, a stubby tail, and a genome size of approximately 50 kb. Replication of ΦGP100 was negatively affected at temperatures higher than 25°C. ΦGP100 had a negative impact on the population size and the biocontrol activity of P. fluorescens strain CHA0-Rif (a rifampicin-resistant variant of CHA0) in natural soil microcosms. In the presence of ΦGP100, the population size of strain CHA0-Rif in soil and on cucumber roots was reduced more than 100-fold. As a consequence, the bacterium's capacity to protect cucumber against a root disease caused by the pathogenic oomycete Pythium ultimum was entirely abolished. In contrast, the phage affected neither root colonization and nor the disease suppressive effect of a ΦGP100-resistant variant of strain CHA0-Rif. To our knowledge, this study is the first to illustrate the potential of phages to impair biocontrol performance of beneficial bacteria released into the natural soil environment.

scholarly journals RpoN (σ54) Controls Production of Antifungal Compounds and Biocontrol Activity in Pseudomonas fluorescens CHA0

2005 ◽  
Vol 18 (3) ◽  
pp. 260-272 ◽  
Author(s):  
Maria Péchy-Tarr ◽  
Mélanie Bottiglieri ◽  
Sophie Mathys ◽  
Kirsten Bang Lejbølle ◽  
Ursula Schnider-Keel ◽  
...  
Keyword(s):  
Pseudomonas Fluorescens ◽  
Fungal Pathogens ◽  
Antibiotic Production ◽  
Nitrogen Sources ◽  
Pythium Ultimum ◽  
Natural Soil ◽  
Root Diseases ◽  
Enhanced Production ◽  
Biocontrol Activity ◽  
Pathogen Suppression

Pseudomonas fluorescens CHA0 is an effective biocontrol agent of root diseases caused by fungal pathogens. The strain produces the antibiotics 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT) that make essential contributions to pathogen suppression. This study focused on the role of the sigma factor RpoN (σ54) in regulation of antibiotic production and biocontrol activity in P. fluorescens. An rpoN in-frame-deletion mutant of CHA0 had a delayed growth, was impaired in the utilization of several carbon and nitrogen sources, and was more sensitive to salt stress. The rpoN mutant was defective for flagella and displayed drastically reduced swimming and swarming motilities. Interestingly, the rpoN mutant showed a severalfold enhanced production of DAPG and expression of the biosynthetic gene phlA compared with the wild type and the mutant complemented with monocopy rpoN+. By contrast, loss of RpoN function resulted in markedly lowered PLT production and plt gene expression, suggesting that RpoN controls the balance of the two antibiotics in strain CHA0. In natural soil microcosms, the rpoN mutant was less effective in protecting cucumber from a root rot caused by Pythium ultimum. Remarkably, the mutant was not significantly impaired in its root colonization capacity, even at early stages of root infection by Pythium spp. Taken together, our results establish RpoN for the first time as a major regulator of biocontrol activity in Pseudomonas fluorescens.

scholarly journals Two Novel MvaT-Like Global Regulators Control Exoproduct Formation and Biocontrol Activity in Root-Associated Pseudomonas fluorescens CHA0

2006 ◽  
Vol 19 (3) ◽  
pp. 313-329 ◽  
Author(s):  
Eric Baehler ◽  
Patrice de Werra ◽  
Lukas Y. Wick ◽  
Maria Péchy-Tarr ◽  
Sophie Mathys ◽  
...  
Keyword(s):  
Pseudomonas Fluorescens ◽  
Double Mutant ◽  
Antibiotic Production ◽  
Pathogenic Fungi ◽  
Pythium Ultimum ◽  
Regulatory Elements ◽  
Wild Type ◽  
Global Regulators ◽  
Root Diseases ◽  
Biocontrol Activity

Pseudomonas fluorescens CHA0 protects various crop plants against root diseases caused by pathogenic fungi. Among a range of exoproducts excreted by strain CHA0, the antifungal compounds 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT) are particularly relevant to the strain's biocontrol potential. Here, we report on the characterization of MvaT and MvaV as novel regulators of biocontrol activity in strain CHA0. We establish the two proteins as further members of an emerging family of MvaT-like regulators in pseudomonads that are structurally and functionally related to the DNA-binding protein H-NS. In mvaT and mvaV in frame-deletion mutants of strain CHA0, PLT production was enhanced about four- and 1.5-fold, respectively, whereas DAPG production remained at wild-type levels. Remarkably, PLT production was increased up to 20-fold in an mvaT mvaV double mutant. DAPG biosynthesis was almost completely repressed in this mutant. The effects on antibiotic production could be confirmed by following expression of gfp-based reporter fusions to the corresponding biosynthetic genes. MvaT and MvaV also influenced levels of other exoproducts, motility, and physicochemical cell-surface properties to various extents. Compared with the wild type, mvaT and mvaV mutants had an about 20% reduced capacity (in terms of plant fresh weight) to protect cucumber from a root rot caused by Pythium ultimum. Biocontrol activity was nearly completely abolished in the double mutant. Our findings indicate that MvaT and MvaV act together as further global regulatory elements in the complex network controlling expression of biocontrol traits in plant-beneficial pseudomonads.

scholarly journals A target expression threshold dictates invader defense and autoimmunity by CRISPR-Cas13

2021 ◽  
Author(s):  
Elena Vialetto ◽  
Yanying Yu ◽  
Scott P. Collins ◽  
Katharina G. Wandera ◽  
Lars Barquist ◽  
...  
Keyword(s):  
Immune Activation ◽  
Rna Degradation ◽  
Lytic Bacteriophage ◽  
Immune Systems ◽  
Expression Levels ◽  
Additional Requirement ◽  
Genome Wide ◽  
A Genome ◽  
Rna Targeting ◽  
Target Transcript

Immune systems must recognize and clear foreign invaders without eliciting autoimmunity. CRISPR-Cas immune systems in prokaryotes manage this task by following two criteria: extensive guide:target complementarity and a defined target-flanking motif. Here we report an additional requirement for RNA-targeting CRISPR-Cas13 systems: expression of the target transcript exceeding a threshold. This finding is based on targeting endogenous non-essential transcripts, which rarely elicited dormancy through collateral RNA degradation. Instead, eliciting dormancy required over-expressing targeted transcripts above a threshold. A genome-wide screen confirmed target expression levels as the principal determinant of cytotoxic autoimmunity and revealed that the threshold shifts with the guide:target pair. This expression threshold ensured defense against a lytic bacteriophage yet allowed tolerance of a targeted beneficial gene expressed from an invading plasmid. These findings establish target expression levels as a third criterion for immune activation by RNA-targeting CRISPR-Cas systems, buffering against autoimmunity and distinguishing pathogenic and benign invaders.

scholarly journals MAPK cascade gene family in Camellia sinensis: In-silico identification, expression profiles and regulatory network analysis

BMC Genomics ◽  
2020 ◽  
Vol 21 (1) ◽  
Author(s):  
Archita Chatterjee ◽  
Abhirup Paul ◽  
G. Meher Unnati ◽  
Ruchika Rajput ◽  
Trisha Biswas ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Camellia Sinensis ◽  
Regulatory Network ◽  
Expression Profiles ◽  
Abiotic Factors ◽  
Mapk Cascade ◽  
Mitogen Activated Protein Kinase ◽  
Functional Study ◽  
A Genome ◽  
Mitogen Activated Protein

Abstract Background Mitogen Activated Protein Kinase (MAPK) cascade is a fundamental pathway in organisms for signal transduction. Though it is well characterized in various plants, there is no systematic study of this cascade in tea. Result In this study, 5 genes of Mitogen Activated Protein Kinase Kinase (MKK) and 16 genes of Mitogen Activated Protein Kinase (MPK) in Camellia sinensis were found through a genome-wide search taking Arabidopsis thaliana as the reference genome. Also, phylogenetic relationships along with structural analysis which includes gene structure, location as well as protein conserved motifs and domains, were systematically examined and further, predictions were validated by the results. The plant species taken for comparative study clearly displayed segmental duplication, which was a significant candidate for MAPK cascade expansion. Also, functional interaction was carried out in C. sinensis based on the orthologous genes in Arabidopsis. The expression profiles linked to various stress treatments revealed wide involvement of MAPK and MAPKK genes from Tea in response to various abiotic factors. In addition, the expression of these genes was analysed in various tissues. Conclusion This study provides the targets for further comprehensive identification, functional study, and also contributed for a better understanding of the MAPK cascade regulatory network in C. sinensis.

Secondary Metabolite- and Endochitinase-Dependent Antagonism toward Plant-Pathogenic Microfungi of Pseudomonas fluorescens Isolates from Sugar Beet Rhizosphere

1998 ◽  
Vol 64 (10) ◽  
pp. 3563-3569 ◽  
Author(s):  
Mette Neiendam Nielsen ◽  
Jan Sørensen ◽  
Johannes Fels ◽  
Hans Christian Pedersen
Keyword(s):  
Biological Control ◽  
Cell Wall ◽  
Sugar Beet ◽  
Pseudomonas Fluorescens ◽  
Secondary Metabolite ◽  
Pythium Ultimum ◽  
Medium Composition ◽  
Fungal Antagonism ◽  
Lipopeptide Antibiotic

ABSTRACT Forty-seven isolates representing all biovars of Pseudomonas fluorescens (biovars I to VI) were collected from the rhizosphere of field-grown sugar beet plants to select candidate strains for biological control of preemergence damping-off disease. The isolates were tested for in vitro antagonism toward the plant-pathogenic microfungi Pythium ultimum and Rhizoctonia solani in three different plate test media. Mechanisms of fungal inhibition were elucidated by tracing secondary-metabolite production and cell wall-degrading enzyme activity in the same media. Most biovars expressed a specific mechanism of antagonism, as represented by a unique antibiotic or enzyme production in the media. A lipopeptide antibiotic, viscosinamide, was produced independently of medium composition by P. fluorescens bv. I, whereas the antibiotic 2,4-diacetylphloroglucinol was observed only in glucose-rich medium and only in P. fluorescens bv. II/IV. Both pathogens were inhibited by the two antibiotics. Finally, in low-glucose medium, a cell wall-degrading endochitinase activity in P. fluorescens bv. I, III, and VI was the apparent mechanism of antagonism toward R. solani. The viscosinamide-producing DR54 isolate (bv. I) was shown to be an effective candidate for biological control, as tested in a pot experiment with sugar beet seedlings infested with Pythium ultimum. The assignment of different patterns of fungal antagonism to the biovars of P. fluorescens is discussed in relation to an improved selection protocol for candidate strains to be used in biological control.

scholarly journals Role of ptsP, orfT, and sss Recombinase Genes in Root Colonization by Pseudomonas fluorescens Q8r1-96

2006 ◽  
Vol 72 (11) ◽  
pp. 7111-7122 ◽  
Author(s):  
Olga V. Mavrodi ◽  
Dmitri V. Mavrodi ◽  
David M. Weller ◽  
Linda S. Thomashow
Keyword(s):  
Pseudomonas Fluorescens ◽  
Fungal Pathogens ◽  
Root Colonization ◽  
Genomic Library ◽  
Wheat Root ◽  
Gene Replacement ◽  
Nitrogen Utilization ◽  
Gaeumannomyces Graminis ◽  
Natural Soil ◽  
Recombinase Gene

ABSTRACT Pseudomonas fluorescens Q8r1-96 produces 2,4-diacetylphloroglucinol (2,4-DAPG), a polyketide antibiotic that suppresses a wide variety of soilborne fungal pathogens, including Gaeumannomyces graminis var. tritici, which causes take-all disease of wheat. Strain Q8r1-96 is representative of the D-genotype of 2,4-DAPG producers, which are exceptional because of their ability to aggressively colonize and maintain large populations on the roots of host plants, including wheat, pea, and sugar beet. In this study, three genes, an sss recombinase gene, ptsP, and orfT, which are important in the interaction of Pseudomonas spp. with various hosts, were investigated to determine their contributions to the unusual colonization properties of strain Q8r1-96. The sss recombinase and ptsP genes influence global processes, including phenotypic plasticity and organic nitrogen utilization, respectively. The orfT gene contributes to the pathogenicity of Pseudomonas aeruginosa in plants and animals and is conserved among saprophytic rhizosphere pseudomonads, but its function is unknown. Clones containing these genes were identified in a Q8r1-96 genomic library, sequenced, and used to construct gene replacement mutants of Q8r1-96. Mutants were characterized to determine their 2,4-DAPG production, motility, fluorescence, colony morphology, exoprotease and hydrogen cyanide (HCN) production, carbon and nitrogen utilization, and ability to colonize the rhizosphere of wheat grown in natural soil. The ptsP mutant was impaired in wheat root colonization, whereas mutants with mutations in the sss recombinase gene and orfT were not. However, all three mutants were less competitive than wild-type P. fluorescens Q8r1-96 in the wheat rhizosphere when they were introduced into the soil by paired inoculation with the parental strain.

scholarly journals Role of Gluconic Acid Production in the Regulation of Biocontrol Traits of Pseudomonas fluorescens CHA0

2009 ◽  
Vol 75 (12) ◽  
pp. 4162-4174 ◽  
Author(s):  
Patrice de Werra ◽  
Maria Péchy-Tarr ◽  
Christoph Keel ◽  
Monika Maurhofer
Keyword(s):  
Pseudomonas Fluorescens ◽  
Gluconic Acid ◽  
Acid Production ◽  
Disease Suppression ◽  
Gaeumannomyces Graminis ◽  
Antifungal Compounds ◽  
Enhanced Production ◽  
Biocontrol Activity ◽  
Gluconic Acid Production

ABSTRACT The rhizobacterium Pseudomonas fluorescens CHA0 promotes the growth of various crop plants and protects them against root diseases caused by pathogenic fungi. The main mechanism of disease suppression by this strain is the production of the antifungal compounds 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT). Direct plant growth promotion can be achieved through solubilization of inorganic phosphates by the production of organic acids, mainly gluconic acid, which is one of the principal acids produced by Pseudomonas spp. The aim of this study was to elucidate the role of gluconic acid production in CHA0. Therefore, mutants were created with deletions in the genes encoding glucose dehydrogenase (gcd) and gluconate dehydrogenase (gad), required for the conversion of glucose to gluconic acid and gluconic acid to 2-ketogluconate, respectively. These enzymes should be of predominant importance for rhizosphere-colonizing biocontrol bacteria, as major carbon sources provided by plant root exudates are made up of glucose. Our results show that the ability of strain CHA0 to acidify its environment and to solubilize mineral phosphate is strongly dependent on its ability to produce gluconic acid. Moreover, we provide evidence that the formation of gluconic acid by CHA0 completely inhibits the production of PLT and partially inhibits that of DAPG. In the Δgcd mutant, which does not produce gluconic acid, the enhanced production of antifungal compounds was associated with improved biocontrol activity against take-all disease of wheat, caused by Gaeumannomyces graminis var. tritici. This study provides new evidence for a close association of gluconic acid metabolism with antifungal compound production and biocontrol activity in P. fluorescens CHA0.

Sign in / Sign up

Export Citation Format

Share Document