The Experts below are selected from a list of 1719 Experts worldwide ranked by ideXlab platform
Linda S Thomashow - One of the best experts on this subject based on the ideXlab platform.
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global landscape of phenazine biosynthesis and biodegradation reveals species specific colonization patterns in agricultural soils and crop microbiomes
eLife, 2020Co-Authors: Daniel Dar, Linda S Thomashow, David M Weller, Dianne K NewmanAbstract:Phenazines are natural bacterial antibiotics that can protect crops from disease. However, for most crops it is unknown which producers and specific Phenazines are ecologically relevant, and whether phenazine biodegradation can counter their effects. To better understand their ecology, we developed and environmentally-validated a quantitative metagenomic approach to mine for phenazine biosynthesis and biodegradation genes, applying it to >800 soil and plant-associated shotgun-metagenomes. We discover novel producer-crop associations and demonstrate that phenazine biosynthesis is prevalent across habitats and preferentially enriched in rhizospheres, whereas biodegrading bacteria are rare. We validate an association between maize and Dyella japonica, a putative producer abundant in crop microbiomes. D. japonica upregulates phenazine biosynthesis during phosphate limitation and robustly colonizes maize seedling roots. This work provides a global picture of Phenazines in natural environments and highlights plant-microbe associations of agricultural potential. Our metagenomic approach may be extended to other metabolites and functional traits in diverse ecosystems.
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recent insights into the diversity frequency and ecological roles of Phenazines in fluorescent pseudomonas spp
Environmental Microbiology, 2013Co-Authors: Dmitri V Mavrodi, David M Weller, Wulf Blankenfeldt, Olga V. Mavrodi, James A. Parejko, Younsig Kwak, Linda S ThomashowAbstract:Phenazine compounds represent a large class of bacterial metabolites that are produced by some fluorescent Pseudomonas spp. and a few other bacterial genera. Phenazines were first noted in the scientific literature over 100 years ago, but for a long time were considered to be pigments of uncertain function. Following evidence that Phenazines act as virulence factors in the opportunistic human and animal pathogen Pseudomonas aeruginosa and are actively involved in the suppression of plant pathogens, interest in these compounds has broadened to include investigations of their genetics, biosynthesis, activity as electron shuttles, and contribution to the ecology and physiology of the cells that produce them. This minireview highlights some recent and exciting insights into the diversity, frequency and ecological roles of Phenazines produced by fluorescent Pseudomonas spp.
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biological control of rhizoctonia root rot on bean by phenazine and cyclic lipopeptide producing pseudomonas cmr12a
Phytopathology, 2011Co-Authors: Jolien Daes, Lars E P Dietrich, Marc Ongena, Gia Khuong Hoang Hua, Dmitri V Mavrodi, Linda S Thomashow, Katrien De Maeyer, Joke Pannecoucque, Ilse Forrez, Monica HöfteAbstract:Pseudomonas CMR12a was previously selected as an efficient biocontrol strain producing Phenazines and cyclic lipopeptides (CLPs). In this study, biocontrol capacity of Pseudomonas CMR12a against Rhizoctonia root rot of bean and the involvement of Phenazines and CLPs in this ability were tested. Two different anastomosis groups (AGs) of Rhizoctonia solani, the intermediately aggressive AG 2-2 and the highly aggressive AG 4 HGI, were included in growth-chamber experiments with bean plants. The wild-type strain CMR12a dramatically reduced disease severity caused by both R. solani AGs. A CLP-deficient and a phenazine-deficient mutant of CMR12a still protected bean plants, albeit to a lesser extent compared with the wild type. Two mutants deficient in both phenazine and CLP production completely lost their biocontrol activity. Disease-suppressive capacity of CMR12a decreased after washing bacteria before application to soil and thereby removing metabolites produced during growth on plate. In addition, microscopic observations revealed pronounced branching of hyphal tips of both R. solani AGs in the presence of CMR12a. More branched and denser mycelium was also observed for the phenazine-deficient mutant; however, neither the CLP-deficient mutant nor the mutants deficient in both CLPs and Phenazines influenced hyphal growth. Together, results demonstrate the involvement of Phenazines and CLPs during Pseudomonas CMR12a-mediated biocontrol of Rhizoctonia root rot of bean.
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biological control of rhizoctonia root rot on bean by phenazine and cyclic lipopeptide producing pseudomonas cmr12a
Phytopathology, 2011Co-Authors: Jolien Daes, Lars E P Dietrich, Marc Ongena, Dmitri V Mavrodi, Linda S Thomashow, Katrien De Maeyer, Joke Pannecoucque, Ilse Forrez, Monica HöfteAbstract:D’aes, J., Hua, G. K. H., De Maeyer, K., Pannecoucque, J., Forrez, I., Ongena, M., Dietrich, L. E. P., Thomashow, L. S., Mavrodi, D. V., and Hofte, M. 2011. Biological control of Rhizoctonia root rot on bean by phenazine- and cyclic lipopeptide-producing Pseudomonas CMR12a. Phytopathology 101:996-1004. Pseudomonas CMR12a was previously selected as an efficient biocontrol strain producing Phenazines and cyclic lipopeptides (CLPs). In this study, biocontrol capacity of Pseudomonas CMR12a against Rhizoctonia root rot of bean and the involvement of Phenazines and CLPs in this ability were tested. Two different anastomosis groups (AGs) of Rhizoctonia solani, the intermediately aggressive AG 2-2 and the highly aggressive AG 4 HGI, were included in growth-chamber experiments with bean plants. The wild-type strain CMR12a dramatically reduced disease severity caused by both R. solani AGs. A CLP-deficient and a phenazine-deficient mutant of CMR12a still protected bean plants, albeit to a lesser extent compared with the wild type. Two mutants deficient in both phenazine and CLP production completely lost their biocontrol activity. Disease-suppressive capacity of CMR12a decreased after washing bacteria before application to soil and thereby removing metabolites produced during growth on plate. In addition, microscopic observations revealed pronounced branching of hyphal tips of both R. solani AGs in the presence of CMR12a. More branched and denser mycelium was also observed for the phenazine-deficient mutant; however, neither the CLP-deficient mutant nor the mutants deficient in both CLPs and Phenazines influenced hyphal growth. Together, results demonstrate the involvement of Phenazines and CLPs during Pseudomonas CMR12amediated biocontrol of Rhizoctonia root rot of bean.
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phenazine compounds in fluorescent pseudomonas spp biosynthesis and regulation
Annual Review of Phytopathology, 2006Co-Authors: Dmitri V Mavrodi, Wulf Blankenfeldt, Linda S ThomashowAbstract:Abstract The Phenazines include upward of 50 pigmented, heterocyclic nitrogen-containing secondary metabolites synthesized by some strains of fluorescent Pseudomonas spp. and a few other bacterial genera. The antibiotic properties of these compounds have been known for over 150 years, but advances within the past two decades have provided significant new insights into the genetics, biochemistry, and regulation of phenazine synthesis, as well as the mode of action and functional roles of these compounds in the environment. This new knowledge reveals conservation of biosynthetic enzymes across genera but raises questions about conserved biosynthetic mechanisms, and sets the stage for improving the performance of phenazine producers used as biological control agents for soilborne plant pathogens.
Dmitri V Mavrodi - One of the best experts on this subject based on the ideXlab platform.
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recent insights into the diversity frequency and ecological roles of Phenazines in fluorescent pseudomonas spp
Environmental Microbiology, 2013Co-Authors: Dmitri V Mavrodi, David M Weller, Wulf Blankenfeldt, Olga V. Mavrodi, James A. Parejko, Younsig Kwak, Linda S ThomashowAbstract:Phenazine compounds represent a large class of bacterial metabolites that are produced by some fluorescent Pseudomonas spp. and a few other bacterial genera. Phenazines were first noted in the scientific literature over 100 years ago, but for a long time were considered to be pigments of uncertain function. Following evidence that Phenazines act as virulence factors in the opportunistic human and animal pathogen Pseudomonas aeruginosa and are actively involved in the suppression of plant pathogens, interest in these compounds has broadened to include investigations of their genetics, biosynthesis, activity as electron shuttles, and contribution to the ecology and physiology of the cells that produce them. This minireview highlights some recent and exciting insights into the diversity, frequency and ecological roles of Phenazines produced by fluorescent Pseudomonas spp.
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Phenazines and bacterial biofilms
2013Co-Authors: Dmitri V Mavrodi, James A. ParejkoAbstract:Most bacteria in the environment exist in biofilms—structured, surface-attached multicellular communities that are enmeshed in a self-produced polysaccharide matrix. Biofilms allow bacteria to participate is social interactions, survive under harsh conditions and successfully resist antimicrobials, invasion by competitors, predation, and destruction by components of the immune system. Fluorescent Pseudomonas spp. are prolific biofilm formers and some members of the genus have become model organisms for the study of biofilm biology. Several economically important groups of pseudomonads produce Phenazines, pigmented, redox-active metabolites that have long been recognized for their broad-spectrum antibiotic activity. The current chapter focuses on the emerging close link between phenazine production and biofilm formation in Pseudomonas spp., and on the important role of Phenazines in biofilms associated with human infectious diseases and highly competitive environmental niches such as soil and the plant rhizosphere.
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biological control of rhizoctonia root rot on bean by phenazine and cyclic lipopeptide producing pseudomonas cmr12a
Phytopathology, 2011Co-Authors: Jolien Daes, Lars E P Dietrich, Marc Ongena, Gia Khuong Hoang Hua, Dmitri V Mavrodi, Linda S Thomashow, Katrien De Maeyer, Joke Pannecoucque, Ilse Forrez, Monica HöfteAbstract:Pseudomonas CMR12a was previously selected as an efficient biocontrol strain producing Phenazines and cyclic lipopeptides (CLPs). In this study, biocontrol capacity of Pseudomonas CMR12a against Rhizoctonia root rot of bean and the involvement of Phenazines and CLPs in this ability were tested. Two different anastomosis groups (AGs) of Rhizoctonia solani, the intermediately aggressive AG 2-2 and the highly aggressive AG 4 HGI, were included in growth-chamber experiments with bean plants. The wild-type strain CMR12a dramatically reduced disease severity caused by both R. solani AGs. A CLP-deficient and a phenazine-deficient mutant of CMR12a still protected bean plants, albeit to a lesser extent compared with the wild type. Two mutants deficient in both phenazine and CLP production completely lost their biocontrol activity. Disease-suppressive capacity of CMR12a decreased after washing bacteria before application to soil and thereby removing metabolites produced during growth on plate. In addition, microscopic observations revealed pronounced branching of hyphal tips of both R. solani AGs in the presence of CMR12a. More branched and denser mycelium was also observed for the phenazine-deficient mutant; however, neither the CLP-deficient mutant nor the mutants deficient in both CLPs and Phenazines influenced hyphal growth. Together, results demonstrate the involvement of Phenazines and CLPs during Pseudomonas CMR12a-mediated biocontrol of Rhizoctonia root rot of bean.
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biological control of rhizoctonia root rot on bean by phenazine and cyclic lipopeptide producing pseudomonas cmr12a
Phytopathology, 2011Co-Authors: Jolien Daes, Lars E P Dietrich, Marc Ongena, Dmitri V Mavrodi, Linda S Thomashow, Katrien De Maeyer, Joke Pannecoucque, Ilse Forrez, Monica HöfteAbstract:D’aes, J., Hua, G. K. H., De Maeyer, K., Pannecoucque, J., Forrez, I., Ongena, M., Dietrich, L. E. P., Thomashow, L. S., Mavrodi, D. V., and Hofte, M. 2011. Biological control of Rhizoctonia root rot on bean by phenazine- and cyclic lipopeptide-producing Pseudomonas CMR12a. Phytopathology 101:996-1004. Pseudomonas CMR12a was previously selected as an efficient biocontrol strain producing Phenazines and cyclic lipopeptides (CLPs). In this study, biocontrol capacity of Pseudomonas CMR12a against Rhizoctonia root rot of bean and the involvement of Phenazines and CLPs in this ability were tested. Two different anastomosis groups (AGs) of Rhizoctonia solani, the intermediately aggressive AG 2-2 and the highly aggressive AG 4 HGI, were included in growth-chamber experiments with bean plants. The wild-type strain CMR12a dramatically reduced disease severity caused by both R. solani AGs. A CLP-deficient and a phenazine-deficient mutant of CMR12a still protected bean plants, albeit to a lesser extent compared with the wild type. Two mutants deficient in both phenazine and CLP production completely lost their biocontrol activity. Disease-suppressive capacity of CMR12a decreased after washing bacteria before application to soil and thereby removing metabolites produced during growth on plate. In addition, microscopic observations revealed pronounced branching of hyphal tips of both R. solani AGs in the presence of CMR12a. More branched and denser mycelium was also observed for the phenazine-deficient mutant; however, neither the CLP-deficient mutant nor the mutants deficient in both CLPs and Phenazines influenced hyphal growth. Together, results demonstrate the involvement of Phenazines and CLPs during Pseudomonas CMR12amediated biocontrol of Rhizoctonia root rot of bean.
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Diversity and evolution of the phenazine biosynthesis pathway
Applied Microbiology and Biotechnology, 2010Co-Authors: Dmitri V Mavrodi, Sylvie Mazurier, Philippe Lemanceau, Wulf Blankenfeldt, Tobin L. Peever, Olga V. Mavrodi, James A. Parejko, Jos M. Raaijmakers, Lutz Heide, David M WellerAbstract:Phenazines are versatile secondary metabolites of bacterial origin that function in biological control of plant pathogens and contribute to the ecological fitness and pathogenicity of the producing strains. In this study, we employed a collection of 94 strains having various geographic, environmental, and clinical origins to study the distribution and evolution of phenazine genes in members of the genera Pseudomonas, Burkholderia, Pectobacterium, Brevibacterium, and Streptomyces. Our results confirmed the diversity of phenazine producers and revealed that most of them appear to be soil-dwelling and/or plant-associated species. Genome analyses and comparisons of phylogenies inferred from sequences of the key phenazine biosynthesis (phzF) and housekeeping (rrs, recA, rpoB, atpD, and gyrB) genes revealed that the evolution and dispersal of phenazine genes are driven by mechanisms ranging from conservation in Pseudomonas spp. to horizontal gene transfer in Burkholderia spp. and Pectobacterium spp. DNA extracted from cereal crop rhizospheres and screened for the presence of phzF contained sequences consistent with the presence of a diverse population of phenazine producers in commercial farm fields located in central Washington state, which provided the first evidence of United States soils enriched in indigenous phenazine-producing bacteria.
Elizabeth A. Pierson - One of the best experts on this subject based on the ideXlab platform.
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Effect of Producing Different Phenazines on Bacterial Fitness and Biological Control in Pseudomonas chlororaphis 30-84
Hanrimwon Publishing Company, 2018Co-Authors: Dongping Wang, Leland S Pierson, Elizabeth A. PiersonAbstract:Pseudomonas chlororaphis 30-84 is a biological control agent selected for its ability to suppress diseases caused by fungal pathogens. P. chlororaphis 30-84 produces three Phenazines: phenazine-1-carboxylic acid (PCA), 2-hydroxy-phenazine-1-carboxylic acid (2OHPCA) and a small amount of 2-hydroxy-phenazine (2OHPHZ), and these are required for fungal pathogen inhibition and wheat rhizosphere competence. The two, 2-hydroxy derivatives are produced from PCA via the activity of a phenazine-modifying enzyme encoded by phzO. In addition to the seven biosynthetic genes responsible for the production of PCA, many other Pseudomonas strains possess one or more modifying genes, which encode enzymes that act independently or together to convert PCA into other phenazine derivatives. In order to understand the fitness effects of producing different Phenazines, we constructed isogenic derivatives of P. chlororaphis 30-84 that differed only in the type of Phenazines produced. Altering the type of Phenazines produced by P. chlororaphis 30-84 enhanced the spectrum of fungal pathogens inhibited and altered the degree of take-all disease suppression. These strains also differed in their ability to promote extracellular DNA release, which may contribute to the observed differences in the amount of biofilm produced. All derivatives were equally important for survival over repeated plant/harvest cycles, indicating that the type of Phenazines produced is less important for persistence in the wheat rhizosphere than whether or not cells produce Phenazines. These findings provide a better understanding of the effects of different Phenazines on functions important for biological control activity with implications for applications that rely on introduced or native phenazine producing populations
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Phenazine production and gene expression patterns.
2018Co-Authors: Dongping Wang, Leland S Pierson, Tessa R. Ries, Elizabeth A. PiersonAbstract:(A) Phenazine production by the 30–84 wild-type (WT) and 30-84Enh in different media (AB minimal, LB and PPMD). Data points represent means of three replicates ± standard error. Asterisks indicate significant differences as determined by unpaired t-test (P < 0.05). Experiments were repeated twice. (B) Expression of the phenazine regulatory genes in 30-84WT and 30-84Enh. The relative expression of selected phz operon (phzX, phzB and phzO) in 30-84WT and 30-84Enh were determined by qPCR using the16s rDNA gene as the reference. (C) Time course of phenazine production by 30-84WT and 30-84Enh in AB-C medium. During the growth, samples were taken periodically and from them total Phenazines were extracted. Data points represent means of three replicates ± standard error. In some cases, error bars do not exceed the size of the symbol. Experiments were repeated twice. (D) AHL production by 30-84WT and 30-84Enh. AHLs obtained from 30-84WT and 30-84Enh were quantified using the AHL-specific reporter strain 30-84I/Z (phzI -, phzB::lacZ). AHLs were quantified based on β-galactosidase activity and reported in Miller Units (MU). Data are the means and standard errors of 8 replicates. Asterisks indicate significant differences as determined by unpaired t-test (P < 0.05). (A) and (C) Phenazines were quantified by UV-visible light spectroscopy at absorbance of 367 nm.
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disruption of miaa provides insights into the regulation of phenazine biosynthesis under suboptimal growth conditions in pseudomonas chlororaphis 30 84
Microbiology, 2017Co-Authors: Dongping Wang, Leland S Pierson, Elizabeth A. PiersonAbstract:Many products of secondary metabolism are activated by quorum sensing (QS), yet even at cell densities sufficient for QS, their production may be repressed under suboptimal growth conditions via mechanisms that still require elucidation. For many beneficial plant-associated bacteria, secondary metabolites such as Phenazines are important for their competitive survival and plant-protective activities. Previous work established that phenazine biosynthesis in Pseudomonas chlororaphis 30-84 is regulated by the PhzR/PhzI QS system, which in turn is regulated by transcriptional regulator Pip, two-component system RpeA/RpeB and stationary phase/stress sigma factor RpoS. Disruption of MiaA, a tRNA modification enzyme, altered primary metabolism and growth leading to widespread effects on secondary metabolism, including reduced phenazine production and oxidative stress tolerance. Thus, the miaA mutant provided the opportunity to examine the regulation of phenazine production in response to altered metabolism and growth or stress tolerance. Despite the importance of MiaA for translation efficiency, the most significant effect of miaA disruption on phenazine production was the reduction in the transcription of phzR, phzI and pip, whereas neither the transcription nor translation of RpeB, a transcriptional regulator of pip, was affected. Constitutive expression of rpeB or pip in the miaA mutant completely restored phenazine production, but it resulted in further growth impairment. Constitutive expression of RpoS alleviated sensitivity to oxidative stress resulting from RpoS translation inefficiency in the miaA mutant, but it did not restore phenazine production. Our results support the model that cells curtail phenazine biosynthesis under suboptimal growth conditions via RpeB/Pip-mediated regulation of QS.
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the phenazine 2 hydroxy phenazine 1 carboxylic acid promotes extracellular dna release and has broad transcriptomic consequences in pseudomonas chlororaphis 30 84
PLOS ONE, 2016Co-Authors: Dongping Wang, Leland S Pierson, Robert J. Dorosky, Elizabeth A. PiersonAbstract:Enhanced production of 2-hydroxy-phenazine-1-carboxylic acid (2-OH-PCA) by the biological control strain Pseudomonas chlororaphis 30–84 derivative 30-84O* was shown previously to promote cell adhesion and alter the three-dimensional structure of surfaceattached biofilms compared to the wild type. The current study demonstrates that production of 2-OH-PCA promotes the release of extracellular DNA, which is correlated with the production of structured biofilm matrix. Moreover, the essential role of the extracellular DNA in maintaining the mass and structure of the 30–84 biofilm matrix is demonstrated. To better understand the role of different Phenazines in biofilm matrix production and gene expression, transcriptomic analyses were conducted comparing gene expression patterns of populations of wild type, 30-84O* and a derivative of 30–84 producing only PCA (30-84PCA) to a phenazine defective mutant (30-84ZN) when grown in static cultures. RNA-Seq analyses identified a group of 802 genes that were differentially expressed by the phenazine producing derivatives compared to 30-84ZN, including 240 genes shared by the two 2-OH-PCA producing derivatives, the wild type and 30-84O*. A gene cluster encoding a bacteriophage- derived pyocin and its lysis cassette was upregulated in 2-OH-PCA producing derivatives. A holin encoded in this gene cluster was found to contribute to the release of eDNA inmore » 30–84 biofilm matrices, demonstrating that the influence of 2-OH-PCA on eDNA production is due in part to cell autolysis as a result of pyocin production and release. The results expand the current understanding of the functions different Phenazines play in the survival of bacteria in biofilm-forming communities.« less
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The Phenazine 2-Hydroxy-Phenazine-1-Carboxylic Acid Promotes Extracellular DNA Release and Has Broad Transcriptomic Consequences in Pseudomonas chlororaphis 30–84
2016Co-Authors: Dongping Wang, Leland S Pierson, Robert J. Dorosky, Elizabeth A. PiersonAbstract:Enhanced production of 2-hydroxy-phenazine-1-carboxylic acid (2-OH-PCA) by the biological control strain Pseudomonas chlororaphis 30–84 derivative 30-84O* was shown previously to promote cell adhesion and alter the three-dimensional structure of surface-attached biofilms compared to the wild type. The current study demonstrates that production of 2-OH-PCA promotes the release of extracellular DNA, which is correlated with the production of structured biofilm matrix. Moreover, the essential role of the extracellular DNA in maintaining the mass and structure of the 30–84 biofilm matrix is demonstrated. To better understand the role of different Phenazines in biofilm matrix production and gene expression, transcriptomic analyses were conducted comparing gene expression patterns of populations of wild type, 30-84O* and a derivative of 30–84 producing only PCA (30-84PCA) to a phenazine defective mutant (30-84ZN) when grown in static cultures. RNA-Seq analyses identified a group of 802 genes that were differentially expressed by the phenazine producing derivatives compared to 30-84ZN, including 240 genes shared by the two 2-OH-PCA producing derivatives, the wild type and 30-84O*. A gene cluster encoding a bacteriophage-derived pyocin and its lysis cassette was upregulated in 2-OH-PCA producing derivatives. A holin encoded in this gene cluster was found to contribute to the release of eDNA in 30–84 biofilm matrices, demonstrating that the influence of 2-OH-PCA on eDNA production is due in part to cell autolysis as a result of pyocin production and release. The results expand the current understanding of the functions different Phenazines play in the survival of bacteria in biofilm-forming communities.
Lars E P Dietrich - One of the best experts on this subject based on the ideXlab platform.
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interdependency of respiratory metabolism and phenazine associated physiology in pseudomonas aeruginosa pa14
Journal of Bacteriology, 2020Co-Authors: Alexa Pricewhelan, William Cole Cornell, Lars E P DietrichAbstract:Extracellular electron transfer (EET), the reduction of compounds that shuttle electrons to distal oxidants, can support bacterial survival when preferred oxidants are not directly accessible. EET has been shown to contribute to virulence in some pathogenic organisms and is required for current generation in mediator-based fuel cells. In several species, components of the electron transport chain (ETC) have been implicated in electron shuttle reduction, raising the question of how shuttling-based metabolism is integrated with primary routes of metabolic electron flow. The clinically relevant bacterium Pseudomonas aeruginosa can utilize carbon sources (i.e., electron donors) covering a broad range of reducing potentials and possesses a branched ETC that can be modulated to optimize respiratory efficiency. It also produces electron shuttles called Phenazines that facilitate intracellular redox balancing, increasing the complexity of its metabolic potential. In this study, we investigated the reciprocal influence of respiratory metabolism and phenazine-associated physiology in P. aeruginosa PA14. We found that phenazine production affects respiratory activity and terminal oxidase gene expression and that carbon source identity influences the mechanisms enabling phenazine reduction. Furthermore, we found that growth in biofilms, a condition for which phenazine metabolism is critical to normal development and redox balancing, affects the composition of the P. aeruginosa phenazine pool. Together, these findings can aid interpretation of P. aeruginosa behavior during host infection and provide inroads to understanding the cross talk between primary metabolism and shuttling-based physiology in the diverse bacteria that carry out EET.IMPORTANCE The clinically relevant pathogen Pseudomonas aeruginosa uses diverse organic compounds as electron donors and possesses multiple enzymes that transfer electrons from central metabolism to O2 These pathways support a balanced intracellular redox state and produce cellular energy. P. aeruginosa also reduces secondary metabolites called Phenazines to promote redox homeostasis and virulence. In this study, we examined the reciprocal relationship between these primary and secondary routes of electron flow. We found that Phenazines affect respiratory function and that the complement of Phenazines produced is strongly affected by growth in assemblages called biofilms. These results provide a more nuanced understanding of P. aeruginosa redox metabolism and may inform strategies for treating persistent infections caused by this bacterium.
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interdependency of respiratory metabolism and phenazine associated physiology in pseudomonas aeruginosa pa14
bioRxiv, 2019Co-Authors: Alexa Pricewhelan, William Cole Cornell, Lars E P DietrichAbstract:ABSTRACT Extracellular electron transfer (EET), the reduction of compounds that shuttle electrons to distal oxidants, can support bacterial survival when preferred oxidants are not directly accessible. EET has been shown to contribute to virulence in some pathogenic organisms and is required for current generation in mediator-based fuel cells. In several species, components of the electron transport chain (ETC) have been implicated in electron shuttle reduction, raising the question of how shuttling-based metabolism is integrated with primary routes of metabolic electron flow. The clinically relevant bacterium Pseudomonas aeruginosa can utilize carbon sources (i.e., electron donors) covering a broad range of reducing potentials and possesses a branched ETC that can be modulated to optimize respiratory efficiency. It also produces electron shuttles called Phenazines that facilitate intracellular redox balancing, increasing the complexity of its metabolic potential. In this study, we investigated the reciprocal influence of respiratory metabolism and phenazine-associated physiology in Pseudomonas aeruginosa PA14. We found that phenazine production affects respiratory activity and terminal oxidase gene expression, and that carbon source identity influences the mechanisms enabling phenazine reduction. Furthermore, we found that growth in biofilms, a condition for which phenazine metabolism is critical to normal development and redox balancing, dramatically affects the composition of the P. aeruginosa phenazine pool. Together, these findings can aid interpretation of P. aeruginosa behavior during host infection and provide inroads to understanding the crosstalk between primary metabolism and shuttling-based physiology in the diverse bacteria that carry out EET. IMPORTANCE Pseudomonas aeruginosa is a major cause of healthcare-associated infections and long-term lung infections in people with cystic fibrosis. It can use diverse organic compounds as electron donors and possesses multiple enzymes that can transfer electrons from central metabolism to O2. These pathways support a balanced intracellular redox state and the production of cellular energy. Under hypoxic conditions, P. aeruginosa can reduce Phenazines, secondary metabolites that also promote redox homeostasis and that contribute to virulence. We asked how these primary and secondary routes of electron flow influence each other. We found that Phenazines affect respiratory function, that the roles of respiratory enzymes in phenazine reduction are highly condition-dependent, and that the complement of Phenazines produced is strongly affected by growth in assemblages called biofilms. These results provide a more nuanced understanding of P. aeruginosa redox metabolism and may inform strategies for treating persistent infections caused by this bacterium.
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phenazine production promotes antibiotic tolerance and metabolic heterogeneity in pseudomonas aeruginosa biofilms
Nature Communications, 2019Co-Authors: Konstanze T Schiessl, Alexa Pricewhelan, Sakila Z Nazia, Bryan Wang, Wei Min, Lars E P DietrichAbstract:Antibiotic efficacy can be antagonized by bioactive metabolites and other drugs present at infection sites. Pseudomonas aeruginosa, a common cause of biofilm-based infections, releases metabolites called Phenazines that accept electrons to support cellular redox balancing. Here, we find that Phenazines promote tolerance to clinically relevant antibiotics, such as ciprofloxacin, in P. aeruginosa biofilms and that this effect depends on the carbon source provided for growth. We couple stable isotope labeling with stimulated Raman scattering microscopy to visualize biofilm metabolic activity in situ. This approach shows that Phenazines promote metabolism in microaerobic biofilm regions and influence metabolic responses to ciprofloxacin treatment. Consistent with roles of specific respiratory complexes in supporting phenazine utilization in biofilms, phenazine-dependent survival on ciprofloxacin is diminished in mutants lacking these enzymes. Our work introduces a technique for the chemical imaging of biosynthetic activity in biofilms and highlights complex interactions between bacterial products, their effects on biofilm metabolism, and the antibiotics we use to treat infections.
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electron shuttling antibiotics structure bacterial communities by modulating cellular levels of c di gmp
Proceedings of the National Academy of Sciences of the United States of America, 2017Co-Authors: Chinweike Okegbe, Alexa Pricewhelan, Blanche L Fields, Stephanie J Cole, Christopher Beierschmitt, Chase J Morgan, Richard C Stewart, Vincent T Lee, Lars E P DietrichAbstract:Diverse organisms secrete redox-active antibiotics, which can be used as extracellular electron shuttles by resistant microbes. Shuttle-mediated metabolism can support survival when substrates are available not locally but rather at a distance. Such conditions arise in multicellular communities, where the formation of chemical gradients leads to resource limitation for cells at depth. In the pathogenic bacterium Pseudomonas aeruginosa PA14, antibiotics called Phenazines act as oxidants to balance the intracellular redox state of cells in anoxic biofilm subzones. PA14 colony biofilms show a profound morphogenic response to Phenazines resulting from electron acceptor-dependent inhibition of ECM production. This effect is reminiscent of the developmental responses of some eukaryotic systems to redox control, but for bacterial systems its mechanistic basis has not been well defined. Here, we identify the regulatory protein RmcA and show that it links redox conditions to PA14 colony morphogenesis by modulating levels of bis-(3',5')-cyclic-dimeric-guanosine (c-di-GMP), a second messenger that stimulates matrix production, in response to phenazine availability. RmcA contains four Per-Arnt-Sim (PAS) domains and domains with the potential to catalyze the synthesis and degradation of c-di-GMP. Our results suggest that phenazine production modulates RmcA activity such that the protein degrades c-di-GMP and thereby inhibits matrix production during oxidizing conditions. RmcA thus forms a mechanistic link between cellular redox sensing and community morphogenesis analogous to the functions performed by PAS-domain-containing regulatory proteins found in complex eukaryotes.
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the pseudomonas aeruginosa efflux pump mexghi opmd transports a natural phenazine that controls gene expression and biofilm development
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Hassan Sakhtah, Alexa Pricewhelan, Deborah A Hogan, Diana K Morales, Leslie Koyama, Yihan Zhang, Blanche L Fields, Kenneth L Shepard, Lars E P DietrichAbstract:Redox-cycling compounds, including endogenously produced phenazine antibiotics, induce expression of the efflux pump MexGHI-OpmD in the opportunistic pathogen Pseudomonas aeruginosa. Previous studies of P. aeruginosa virulence, physiology, and biofilm development have focused on the blue phenazine pyocyanin and the yellow phenazine-1-carboxylic acid (PCA). In P. aeruginosa phenazine biosynthesis, conversion of PCA to pyocyanin is presumed to proceed through the intermediate 5-methylphenazine-1-carboxylate (5-Me-PCA), a reactive compound that has eluded detection in most laboratory samples. Here, we apply electrochemical methods to directly detect 5-Me-PCA and find that it is transported by MexGHI-OpmD in P. aeruginosa strain PA14 planktonic and biofilm cells. We also show that 5-Me-PCA is sufficient to fully induce MexGHI-OpmD expression and that it is required for wild-type colony biofilm morphogenesis. These physiological effects are consistent with the high redox potential of 5-Me-PCA, which distinguishes it from other well-studied P. aeruginosa Phenazines. Our observations highlight the importance of this compound, which was previously overlooked due to the challenges associated with its detection, in the context of P. aeruginosa gene expression and multicellular behavior. This study constitutes a unique demonstration of efflux-based self-resistance, controlled by a simple circuit, in a Gram-negative pathogen.
Monica Höfte - One of the best experts on this subject based on the ideXlab platform.
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Role of Phenazines and cyclic lipopeptides produced by pseudomonas sp. CMR12a in induced systemic resistance on rice and bean
Environmental microbiology reports, 2016Co-Authors: Gia Khuong Hoang Hua, Marc Ongena, Monica HöfteAbstract:Pseudomonas sp. CMR12a produces two different classes of cyclic lipopeptides (CLPs) (orfamides and sessilins), which all play a role in direct antagonism against soilborne pathogens. Here we show that Pseudomonas sp. CMR12a is also able to induce systemic resistance to Magnaporthe oryzae on rice and to the web blight pathogen Rhizoctonia solani AG2-2 on bean. Plant assays with biosynthesis mutants of Pseudomonas sp. CMR12a impaired in the production of Phenazines and/or CLPs and purified metabolites revealed that distinct bacterial determinants are responsible for inducing systemic resistance in these two pathosystems. In rice, mutants impaired in phenazine production completely lost their ability to induce systemic resistance, while a soil drench with pure phenazine-1-carboxamide (PCN) at a concentration of 0.1 or 1 μM was active in inducing resistance against M. oryzae. In bean, mutants that only produced Phenazines, sessilins or orfamides were still able to induce systemic resistance against Rhizoctonia web blight, but a balanced production of these metabolites was needed. This study not only shows that Pseudomonas sp. CMR12a can protect rice to blast disease and bean to web blight disease, but also displays that the determinants involved in induced systemic resistance are plant, pathogen and concentration dependent.
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Interplay between orfamides, sessilins and Phenazines in the control of Rhizoctonia diseases by Pseudomonas sp. CMR12a.
Environmental microbiology reports, 2015Co-Authors: Feyisara Eyiwumi Olorunleke, Gia Khuong Hoang Hua, Nam Phuong Kieu, Monica HöfteAbstract:We investigated the role of Phenazines and cyclic lipopeptides (CLPs) (orfamides and sessilins), antagonistic metabolites produced by Pseudomonas sp. CMR12a, in the biological control of damping-off disease on Chinese cabbage (Brassica chinensis) caused by Rhizoctonia solani AG 2-1 and root rot disease on bean (Phaseolus vulgaris L.) caused by R. solani AG 4-HGI. A Pseudomonas mutant that only produced Phenazines suppressed damping-off disease on Chinese cabbage to the same extent as CMR12a, while its efficacy to reduce root rot on bean was strongly impaired. In both pathosystems, the phenazine mutant that produced both CLPs was equally effective, but mutants that produced only one CLP lost biocontrol activity. In vitro microscopic assays revealed that mutants that only produced sessilins or orfamides inhibited mycelial growth of R. solani when applied together, while they were ineffective on their own. Phenazine-1-carboxamide suppressed mycelial growth of R. solani AG 2-1 but had no effect on AG 4-HGI. Orfamide B suppressed mycelial growth of both R. solani anastomosis groups in a dose-dependent way. Our results point to an additive interaction between both CLPs. Moreover, Phenazines alone are sufficient to suppress Rhizoctonia disease on Chinese cabbage, while they need to work in tandem with the CLPs on bean.
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the involvement of Phenazines and cyclic lipopeptide sessilin in biocontrol of rhizoctonia root rot on bean phaseolus vulgaris by pseudomonas sp cmr12a is influenced by substrate composition
Plant and Soil, 2015Co-Authors: Gia Khuong Hoang Hua, Monica HöfteAbstract:Pseudomonas sp. CMR12a is an effective biocontrol agent that produces various antifungal metabolites including phenazine antibiotics and cyclic lipopeptides. In this study, we wanted to investigate the influence of substrate composition on the role of Phenazines and the cyclic lipopeptide (CLP) sessilin in biocontrol of bean root rot caused by Rhizoctonia solani AG 2–2. Disease severity and spreading rate of R. solani were determined in three substrates, containing different ratios of potting soil and sand, inoculated with Pseudomonas sp. CMR12a or its mutants impaired in phenazine and/or sessilin biosynthesis. In the mixtures containing 50 or 75 % of potting soil, the presence of either Phenazines or sessilin was sufficient to suppress bean root rot. However, in the mixture containing only 25 % of potting soil, the involvement of both compounds was required to provide better protection. The ratio between potting soil and sand also determined the spreading rate of Rhizoctonia hyphae. The mixture containing 75 % of potting soil was the most suppressive against R. solani invasion. The use of various potting soil/sand combinations affected the development of bean root rot disease but Pseudomonas sp. CMR12a effectively controlled the disease in all substrates. Depending on the disease pressure, however, the production of either Phenazines or sessilin, or both compounds is required for effective biocontrol.
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biological control of rhizoctonia root rot on bean by phenazine and cyclic lipopeptide producing pseudomonas cmr12a
Phytopathology, 2011Co-Authors: Jolien Daes, Lars E P Dietrich, Marc Ongena, Gia Khuong Hoang Hua, Dmitri V Mavrodi, Linda S Thomashow, Katrien De Maeyer, Joke Pannecoucque, Ilse Forrez, Monica HöfteAbstract:Pseudomonas CMR12a was previously selected as an efficient biocontrol strain producing Phenazines and cyclic lipopeptides (CLPs). In this study, biocontrol capacity of Pseudomonas CMR12a against Rhizoctonia root rot of bean and the involvement of Phenazines and CLPs in this ability were tested. Two different anastomosis groups (AGs) of Rhizoctonia solani, the intermediately aggressive AG 2-2 and the highly aggressive AG 4 HGI, were included in growth-chamber experiments with bean plants. The wild-type strain CMR12a dramatically reduced disease severity caused by both R. solani AGs. A CLP-deficient and a phenazine-deficient mutant of CMR12a still protected bean plants, albeit to a lesser extent compared with the wild type. Two mutants deficient in both phenazine and CLP production completely lost their biocontrol activity. Disease-suppressive capacity of CMR12a decreased after washing bacteria before application to soil and thereby removing metabolites produced during growth on plate. In addition, microscopic observations revealed pronounced branching of hyphal tips of both R. solani AGs in the presence of CMR12a. More branched and denser mycelium was also observed for the phenazine-deficient mutant; however, neither the CLP-deficient mutant nor the mutants deficient in both CLPs and Phenazines influenced hyphal growth. Together, results demonstrate the involvement of Phenazines and CLPs during Pseudomonas CMR12a-mediated biocontrol of Rhizoctonia root rot of bean.
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biological control of rhizoctonia root rot on bean by phenazine and cyclic lipopeptide producing pseudomonas cmr12a
Phytopathology, 2011Co-Authors: Jolien Daes, Lars E P Dietrich, Marc Ongena, Dmitri V Mavrodi, Linda S Thomashow, Katrien De Maeyer, Joke Pannecoucque, Ilse Forrez, Monica HöfteAbstract:D’aes, J., Hua, G. K. H., De Maeyer, K., Pannecoucque, J., Forrez, I., Ongena, M., Dietrich, L. E. P., Thomashow, L. S., Mavrodi, D. V., and Hofte, M. 2011. Biological control of Rhizoctonia root rot on bean by phenazine- and cyclic lipopeptide-producing Pseudomonas CMR12a. Phytopathology 101:996-1004. Pseudomonas CMR12a was previously selected as an efficient biocontrol strain producing Phenazines and cyclic lipopeptides (CLPs). In this study, biocontrol capacity of Pseudomonas CMR12a against Rhizoctonia root rot of bean and the involvement of Phenazines and CLPs in this ability were tested. Two different anastomosis groups (AGs) of Rhizoctonia solani, the intermediately aggressive AG 2-2 and the highly aggressive AG 4 HGI, were included in growth-chamber experiments with bean plants. The wild-type strain CMR12a dramatically reduced disease severity caused by both R. solani AGs. A CLP-deficient and a phenazine-deficient mutant of CMR12a still protected bean plants, albeit to a lesser extent compared with the wild type. Two mutants deficient in both phenazine and CLP production completely lost their biocontrol activity. Disease-suppressive capacity of CMR12a decreased after washing bacteria before application to soil and thereby removing metabolites produced during growth on plate. In addition, microscopic observations revealed pronounced branching of hyphal tips of both R. solani AGs in the presence of CMR12a. More branched and denser mycelium was also observed for the phenazine-deficient mutant; however, neither the CLP-deficient mutant nor the mutants deficient in both CLPs and Phenazines influenced hyphal growth. Together, results demonstrate the involvement of Phenazines and CLPs during Pseudomonas CMR12amediated biocontrol of Rhizoctonia root rot of bean.