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David M Weller - One of the best experts on this subject based on the ideXlab platform.

  • Rhizosphere Competence of Wild-Type and Genetically Engineered Pseudomonas brassicacearum Is Affected by the Crop Species
    Phytopathology, 2016
    Co-Authors: Stacey Blouin Bankhead, Linda S. Thomashow, David M Weller
    Abstract:

    2,4-Diacetylphloroglucinol (2,4-DAPG)-producing Pseudomonas brassicacearum Q8r1-96 is a highly effective biocontrol agent of take-all disease of wheat. Strain Z30-97, a recombinant derivative of Q8r1-96 containing the phzABCDEFG operon from P. synxantha (formerly P. fluorescens) 2-79 inserted into its chromosome, also produces phenazine-1-carboxylic acid. Rhizosphere population sizes of Q8r1-96, Z30-97, and 2-79, introduced into the soil, were assayed during successive growth cycles of barley, navy bean, or pea under controlled conditions as a measure of the impact of crop species on Rhizosphere colonization of each strain. In the barley Rhizosphere, Z30-96 colonized less that Q8r1-96 when they were introduced separately, and Q8r1-96 out-competed Z30-96 when the strains were introduced together. In the navy bean Rhizosphere, Q8r1-96 colonized better than Z30-97 when the strains were introduced separately. However, both strains had similar population densities when introduced together. Strain Q8r1-96 and Z30-97 colonized the pea Rhizosphere equally well when each strain was introduced separately, but Z30-97 out-competed Q8r1-96 when they were introduced together. To our knowledge, this is the first report of a recombinant biocontrol strain of Pseudomonas spp. gaining Rhizosphere competitiveness on a crop species. When assessing the potential fate of and risk posed by a recombinant Pseudomonas sp. in soil, both the identity of the introduced genes and the crop species colonized by the recombinant strain need to be considered.

  • pseudomonas biocontrol agents of soilborne pathogens looking back over 30 years
    Phytopathology, 2007
    Co-Authors: David M Weller
    Abstract:

    ABSTRACT Pseudomonas spp. are ubiquitous bacteria in agricultural soils and have many traits that make them well suited as biocontrol agents of soilborne pathogens. Tremendous progress has been made in characterizing the process of root colonization by pseudomonads, the biotic and abiotic factors affecting colonization, bacterial traits and genes contributing to Rhizosphere Competence, and the mechanisms of pathogen suppression. This review looks back over the last 30 years of Pseudomonas biocontrol research and highlights key studies, strains, and findings that have had significant impact on shaping our current understanding of biological control by bacteria and the direction of future research.

  • Utilization of trehalose, benzoate, valerate, and seed and root exudates by genotypes of 2,4-diacetylphloroglucinol producing Pseudomonas fluorescens
    Soil Biology and Biochemistry, 2007
    Co-Authors: Leonardo De La Fuente, Dmitri V. Mavrodi, Linda S. Thomashow, David M Weller
    Abstract:

    Abstract Isolates of Pseudomonas fluorescens producing the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) are effective biocontrol agents against soilborne pathogens. A previous study showed that the superior (“premier”) root colonizer P. fluorescens Q8r1-96 (genotype D) utilized trehalose, benzoate and valerate as sole carbon sources but average colonizers Q2-87 (genotype B) and 1M1-96 (genotype L) did not. We tested the utilization of these three carbon sources by a collection of 55 2,4-DAPG-producing P. fluorescens strains from 17 genotypes and found no correlation between a strain's ability to utilize these carbon sources and superior Rhizosphere Competence on wheat and pea. Of the strains tested, 73%, 48% and 69% were able to utilize trehalose, benzoate and valerate as sole carbon sources, respectively. With some exceptions, we found a correlation between the utilization of these compounds and previous groupings of these strains by BOX-PCR; genotype D strains utilized all three compounds. Twenty-three strains grew efficiently on root and seed exudates from wheat and pea, with doubling times between 0.9 and 1.6 h generation −1 and lag phases between 5 and 8 h, comparable to growth on glucose as a sole carbon source. Only 10 strains, including those with “premier” (Q8r1-96) and “average” (Q2-87) Rhizosphere Competence, showed slower growth in wheat root exudates, with lag phases between 16 and 22 h. Results were the same when soil was added to the culture medium. Growth of four strains in media containing glucose or wheat or pea seed exudates as a sole carbon source was not influenced by whether the bacterial cells used as inoculum were harvested from wheat seeds or broth culture. We conclude that the superior ability of some strains to colonize the roots of certain crops cannot be explained by the utilization of the carbon sources tested in our study.

  • minimal changes in rhizobacterial population structure following root colonization by wild type and transgenic biocontrol strains
    FEMS Microbiology Ecology, 2004
    Co-Authors: Stacey Blouin Bankhead, David M Weller, Blanca B. Landa, Elizabeth Lutton, Brian Mcspadden B Gardener
    Abstract:

    Pseudomonas fluorescens strains 2-79, Q8r1-96, and a recombinant strain, Z30-97, produce the antibiotics phenazine-1-carboxylic acid (PCA), 2,4-diacetylphloroglucinol (DAPG), or both antibiotics, respectively. Rhizosphere colonization by these strains and subsequent alterations of bacterial community structure were assayed over multiple growth cycles of wheat under controlled conditions. While added to soil at just log 4 cells per gram prior to planting, all four strains subsequently colonized germinating wheat roots to levels in excess of log 6.5 cells per g (f.w.). Strain-specific differences in Rhizosphere Competence were observed, but these were not generally related to the chromosomal insertion of the phz genes. Multiple differences in bacterial community structure were detected among treatments in each cycle; however, the large majority of changes were not consistently related to the abundance of inoculant strains in the Rhizosphere nor the genetic make-up of the inoculant strains. Nonetheless, T-RFLP profiles of amplified 16S eubacterial sequences indicated that, when compared to the untreated samples, inoculation with Z30-97 resulted in several shifts in Rhizosphere bacterial community structure previously associated with decreased levels of root disease. 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

  • Interactions Between Strains of 2,4-Diacetylphloroglucinol-Producing Pseudomonas fluorescens in the Rhizosphere of Wheat.
    Phytopathology, 2003
    Co-Authors: Blanca B. Landa, Linda S. Thomashow, Dmitri M. Mavrodi, David M Weller
    Abstract:

    Landa, B. B., Mavrodi, D. M., Thomashow, L. S., and Weller, D. M. 2003. Interactions between strains of 2,4-diacetylphloroglucinol-producing Pseudomonas fluorescens in the Rhizosphere of wheat. Phytopathology 93:982-994. Strains of fluorescent Pseudomonas spp. that produce the antibiotic 2,4-diacetylphoroglucinol (2,4-DAPG) are among the most effective rhizobacteria controlling diseases caused by soilborne pathogens. The genotypic diversity that exists among 2,4-DAPG producers can be exploited to improve Rhizosphere Competence and biocontrol activity. Knowing that D-genotype 2,4-DAPG-producing strains are enriched in some take-all decline soils and that P. fluorescens Q8r1-96, a representative D-genotype strain, as defined by whole-cell repetitive sequencebased polymerase chain reaction (rep-PCR) with the BOXA1R primer, is a superior colonizer of wheat roots, we analyzed whether the exceptional Rhizosphere Competence of strain Q8r1-96 on wheat is characteristic of other D-genotype isolates. The Rhizosphere population densities of four D-genotype strains and a K-genotype strain introduced individually into the soil were significantly greater than the densities of four strains belonging to other genotypes (A, B, and L) and remained above log 6.8 CFU/g of root over a 30-week cycling experiment in which wheat was grown for 10 successive cycles of 3 weeks each. We also explored the competitive interactions between strains of different genotypes inhabiting the same soil or Rhizosphere when coinoculated into the soil. Strain Q8r1-96 became dominant in the Rhizosphere and in nonRhizosphere soil during a 15-week cycling experiment when mixed in a 1:1 ratio with either strain Pf-5 (A genotype), Q2-87 (B genotype), or 1M1-96 (L genotype). Furthermore, the use of the de Wit replacement series demonstrated a competitive disadvantage for strain Q2-87 or strong antagonism by strain Q8r1-96 against Q2-87 in the wheat Rhizosphere. Amplified rDNA restriction analysis and sequence analysis of 16S rDNA showed that species of Arthrobacter, Chryseobacterium, Flavobacterium, Massilia, Microbacterium, and Ralstonia also were enriched in culturable populations from the Rhizosphere of wheat at the end of a 30-week cycling experiment in the presence of 2,4-DAPG producers. Identifying the interactions among 2,4-DAPG producers and with other indigenous bacteria in the wheat Rhizosphere will help to elucidate the variability in biocontrol efficacy of introduced 2,4-DAPG producers and fluctuations in the robustness of take-all suppressive soils.

Khaled A. El-tarabily - One of the best experts on this subject based on the ideXlab platform.

  • Promotion of tomato (Lycopersicon esculentum Mill.) plant growth by Rhizosphere competent 1-aminocyclopropane-1-carboxylic acid deaminase-producing streptomycete actinomycetes
    Plant and Soil, 2008
    Co-Authors: Khaled A. El-tarabily
    Abstract:

    The ability of streptomycete actinomycetes to promote growth of tomato through the production of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase was evaluated under gnotobiotic and greenhouse conditions. To achieve this, 64 isolates of Streptomyces spp. obtained from a tomato Rhizosphere in the United Arab Emirates were initially selected for their ability to produce ACC deaminase as well as indole-3-acetic acid (IAA) and subsequently for their Rhizosphere Competence as root colonizers. Of the two selected ACC deaminase-producing isolates showing exceptional Rhizosphere Competence, S. filipinensis no. 15 produced both ACC deaminase and IAA, whilst S. atrovirens no. 26 did not produce IAA. Under greenhouse conditions, the application of S. filipinensis no. 15 or S. atrovirens no. 26 resulted in the reduction of the endogenous levels of ACC, the immediate precursor of ethylene, in both roots and shoots and increased plant growth. Plant growth promotion was most pronounced in the presence of S. filipinensis no. 15 compared to S. atrovirens no. 26. This relative superiority in performance shows the advantage conferred to S. filipinensis no. 15 due to its ability to produce both IAA and ACC deaminase. In comparison, an ACC deaminase-producing isolate of S. albovinaceus no. 41 which was neither Rhizosphere-competent nor capable of producing IAA, failed to promote plant growth compared to S. filipinensis no. 15 or S. atrovirens no. 26 although the growth promotion obtained by S. albovinaceus no. 41 was significant compared to control. The application of S. globosus no. 8, which was not Rhizosphere-competent and did not produce detectable levels of ACC deaminase or IAA did not promote plant growth. These results indicate the importance of Rhizosphere Competence. In conclusion I report the production of ACC deaminase by streptomycete actinomycetes and its ability to enhance plant growth through reduction in the in planta levels of endogenous ACC and the consequent lowering of endogenous ethylene levels in plant tissues.

  • Promotion of growth of bean (Phaseolus vulgaris L.) in a calcareous soil by a phosphate-solubilizing, Rhizosphere-competent isolate of Micromonospora endolithica
    Applied Soil Ecology, 2008
    Co-Authors: Khaled A. El-tarabily, Amr H. Nassar, Krishnapillai Sivasithamparam
    Abstract:

    The aim of this study was to determine the potential of non-streptomycete actinomycetes (NSA) to solubilize insoluble phosphates in soil and to promote plant growth. Thirty-one NSA were isolated using Streptomyces phage and dry heat techniques, from a calcareous soil deficient in available phosphorus (P) in the United Arab Emirates. Nine of these NSA isolates solubilized powdered rock phosphate (PRP) in solid and liquid media. Five isolates were initially selected based on their Rhizosphere Competence. Among them, an isolate of Micromonospora endolithica caused a significant drop in pH in a liquid medium amended with PRP, solubilized considerable amounts of P, produced acid and alkaline phosphatases, as well as a variety of organic acids. In addition, this isolate of M. endolithica was chosen from among the five isolates because it also showed exceptional Rhizosphere Competence and a strong ability to colonize bean (Phaseolus vulgaris L.) roots up to a depth of 14 cm. In the greenhouse, the application of M. endolithica to soil amended with either single super-phosphate (SP) or PRP significantly promoted the growth of roots and shoots of bean plants compared with those of plants grown in non-inoculated soil amended with SP or PRP. This was also evident in the significant increases in the concentration of available P in the soil and in the levels of N, P, K, S, Mg, Fe and Zn in the roots and those of N, P, K, S, Mg and Fe in the shoots of inoculated plants. The plant growth promotion by M. endolithica was most pronounced in the presence of SP as soil amendment compared to PRP. In comparison, a non-phosphate-solubilizing, non-Rhizosphere-competent NSA isolate of M. olivasterospora failed to increase available soil P, nutrient levels in roots and shoots or to promote plant growth. Plant growth regulators tested do not appear to be involved in the plant growth stimulation observed. Neither M. endolithica nor M. olivasterospora produced detectable levels of indole-acetic acid, indole-pyruvic acid, gibberellic acid, isopentenyl adenine, isopentenyl adenoside or zeatin in vitro. This study is the first published report to demonstrate the potential of phosphate-solubilizing NSA to promote plant growth. In addition, it is also the first published report of Rhizosphere-competent actinomycetes capable of solubilizing SP or PRP, in soils.

  • Rhizosphere-competent isolates of streptomycete and non-streptomycete actinomycetes capable of producing cell-wall-degrading enzymes to control Pythium aphanidermatum damping-off disease of cucumber
    Canadian Journal of Botany, 2006
    Co-Authors: Khaled A. El-tarabily
    Abstract:

    Fifty-eight streptomycete and 35 non-streptomycete actinomycetes were isolated from cucumber Rhizosphere soil. These isolates were screened for the production of cell-wall-degrading enzymes using mycelial (Pythium aphanidermatum (Edson) Fitzp.) fragment agar. Eighteen promising isolates were screened for their Competence as root colonizers. Eight isolates showing exceptional Rhizosphere Competence significantly inhibited, in vitro, P. aphanidermatum, the causal agent of postemergence damping-off of cucumber (Cucumis sativus L.) seedlings. The four most inhibitory isolates (Actinoplanes philippinensis Couch, Microbispora rosea Nonomura and Ohara, Micromonospora chalcea (Foulerton) Orskov, and Streptomyces griseoloalbus (Kudrina) Pridham et al.) produced in vitro β-1,3-, β-1,4-, and β-1,6-glucanases and caused lysis of P. aphanidermatum hyphae. None of these produced volatile inhibitors or siderophores. Only S. griseoloalbus produced diffusible inhibitory metabolites, whilst A. philippinensis and Micromonos...

Kornelia Smalla - One of the best experts on this subject based on the ideXlab platform.

  • Rhizosphere Competence and Biocontrol Effect of Pseudomonas sp. RU47 Independent from Plant Species and Soil Type at the Field Scale.
    Frontiers in microbiology, 2018
    Co-Authors: Susanne Schreiter, Kornelia Smalla, Doreen Babin, Rita Grosch
    Abstract:

    Biocontrol inoculants often show inconsistency in their efficacy at field scale and the reason for this remains often unclear. A high Rhizosphere Competence of inoculant strains is assumed to be a key factor for successful biocontrol effects as the biocontrol strain has to compete with the indigenous microbial community in the Rhizosphere. It is known that many factors, among them plant species and soil type shape the Rhizosphere microbial community composition. However, microbial community composition in the Rhizosphere can also be influenced by the presence of a pathogen. We hypothesized that plant species, soil type, and a pathogen affect the Rhizosphere Competence of a biocontrol strain and its biocontrol effect against a soil-borne pathogen. To test the hypothesis, we used an experimental plot system with three soil types (diluvial sand, alluvial loam, loess loam) kept under similar agricultural management at the same field site for 12 years. We investigate the Rhizosphere Competence of Pseudomonas sp. RU47 in two plant species (potato and lettuce) and its biocontrol effect against Rhizoctonia diseases. The colonization density of a rifampicin resistant mutant of RU47 in the Rhizosphere of both crops was evaluated by plate counts. Bacterial community compositions were analyzed by denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene fragments amplified from total community DNA. The inoculant RU47 was able to colonize the Rhizosphere of both model crops in a sufficient density and to reduce disease severity of black scurf on potato and bottom rot on lettuce in all three soils. DGGE indicated that RU47 affected the bacterial community composition stronger in the Rhizosphere of lettuce than in the potato Rhizosphere. In contrast, the effect of the pathogen Rhizoctonia solani on the bacterial community was much stronger in the Rhizosphere of potato than in the lettuce Rhizosphere. A significant effect of RU47 on the Pseudomonas-specific gacA fingerprints of the Rhizosphere was only observed in lettuce in alluvial soil. The soil type and plant species independent biocontrol effects of RU47 and its minor influence on the indigenous bacterial community composition might be important criteria for the registration and use of RU47 as biocontrol strain.

  • Soil type dependent Rhizosphere Competence and biocontrol of two bacterial inoculant strains and their effects on the Rhizosphere microbial community of field-grown lettuce.
    PloS one, 2014
    Co-Authors: Susanne Schreiter, Martin Sandmann, Kornelia Smalla, Rita Grosch
    Abstract:

    Rhizosphere Competence of bacterial inoculants is assumed to be important for successful biocontrol. Knowledge of factors influencing Rhizosphere Competence under field conditions is largely lacking. The present study is aimed to unravel the effects of soil types on the Rhizosphere Competence and biocontrol activity of the two inoculant strains Pseudomonas jessenii RU47 and Serratia plymuthica 3Re4-18 in field-grown lettuce in soils inoculated with Rhizoctonia solani AG1-IB or not. Two independent experiments were carried out in 2011 on an experimental plot system with three soil types sharing the same cropping history and weather conditions for more than 10 years. Rifampicin resistant mutants of the inoculants were used to evaluate their colonization in the Rhizosphere of lettuce. The Rhizosphere bacterial community structure was analyzed by denaturing gradient gel electrophoresis of 16S rRNA gene fragments amplified from total community DNA to get insights into the effects of the inoculants and R. solani on the indigenous Rhizosphere bacterial communities. Both inoculants showed a good colonization ability of the Rhizosphere of lettuce with more than 106 colony forming units per g root dry mass two weeks after planting. An effect of the soil type on Rhizosphere Competence was observed for 3Re4-18 but not for RU47. In both experiments a comparable Rhizosphere Competence was observed and in the presence of the inoculants disease symptoms were either significantly reduced, or at least a non-significant trend was shown. Disease severity was highest in diluvial sand followed by alluvial loam and loess loam suggesting that the soil types differed in their conduciveness for bottom rot disease. Compared to effect of the soil type of the Rhizosphere bacterial communities, the effects of the pathogen and the inoculants were less pronounced. The soil types had a surprisingly low influence on Rhizosphere Competence and biocontrol activity while they significantly affected the bottom rot disease severity.

  • Soil type dependent Rhizosphere Competence and biocontrol of two bacterial inoculant strains and their effects on the Rhizosphere microbial community of field-grown lettuce
    2014
    Co-Authors: Susanne Schreiter, Kornelia Smalla, Martin S, Rita Grosch
    Abstract:

    Rhizosphere Competence of bacterial inoculants is assumed to be important for successful biocontrol. Knowledge of factors influencing Rhizosphere Competence under field conditions is largely lacking. The present study is aimed to unravel the effects of soil types on the Rhizosphere Competence and biocontrol activity of the two inoculant strains Pseudomonas jessenii RU47 and Serratia plymuthica 3Re4-18 in field-grown lettuce in soils inoculated with Rhizoctonia solani AG1-IB or not. Two independent experiments were carried out in 2011 on an experimental plot system with three soil types sharing the same cropping history and weather conditions for more than 10 years. Rifampicin resistant mutants of the inoculants were used to evaluate their colonization in the Rhizosphere of lettuce. The Rhizosphere bacterial community structure was analyzed by denaturing gradient gel electrophoresis of 16S rRNA gene fragments amplified from total community DNA to get insights into the effects of the inoculants and R. solani on the indigenous Rhizosphere bacterial communities. Both inoculants showed a good colonization ability of the Rhizosphere of lettuce with more than 106 colony forming units per g root dry mass two weeks after planting. An effect of the soil type on Rhizosphere Competence was observed for 3Re4-18 but not for RU47. In both experiments a comparable Rhizosphere Competence was observed and in the presence of the inoculants disease symptoms were either significantly reduced, or at least a non-significant trend was shown. Disease severity was highest in diluvial sand followed by alluvial loam and loess loam suggesting that the soil types differed in thei

  • in vitro antagonists of rhizoctonia solani tested on lettuce Rhizosphere Competence biocontrol efficiency and Rhizosphere microbial community response
    FEMS Microbiology Ecology, 2009
    Co-Authors: Modupe F Adesina, Rita Grosch, Antje Lembke, Tzenko D Vatchev, Kornelia Smalla
    Abstract:

    The Rhizosphere Competence of 15 in vitro antagonists of Rhizoctonia solani was determined 4 weeks after sowing inoculated lettuce seeds into nonsterile soil. Based on the colonization ability determined by selective plating, eight strains were selected for growth chamber experiments to determine their efficacy in controlling bottom rot caused by R. solani on lettuce. Although in the first experiment all antagonists colonized the Rhizosphere of lettuce with CFU counts above 2 × 106 g−1 of root fresh weight, only four isolates significantly reduced disease severity. In subsequent experiments involving these four antagonists, only Pseudomonas jessenii RU47 showed effective and consistent disease suppression. Plate counts and denaturing gradient gel electrophoresis (DGGE) fingerprints of Pseudomonas-specific gacA genes amplified from total community DNA confirmed that RU47 established as the dominant Pseudomonas population in the Rhizosphere of inoculated lettuce plants. Furthermore, the DGGE fingerprint revealed that R. solani AG1-IB inoculation severely affected the bacterial and fungal community structure in the Rhizosphere of lettuce and that these effects were much less pronounced in the presence of RU47. Although the exact mechanism of antagonistic activity and the ecology of RU47 remain to be further explored, our results suggest that RU47 is a promising agent to control bottom rot of lettuce.

  • in vitro antagonists of rhizoctonia solani tested on lettuce Rhizosphere Competence biocontrol efficiency and Rhizosphere microbial community response
    FEMS Microbiology Ecology, 2009
    Co-Authors: Modupe F Adesina, Rita Grosch, Antje Lembke, Tzenko D Vatchev, Kornelia Smalla
    Abstract:

    The Rhizosphere Competence of 15 in vitro antagonists of Rhizoctonia solani was determined 4 weeks after sowing inoculated lettuce seeds into nonsterile soil. Based on the colonization ability determined by selective plating, eight strains were selected for growth chamber experiments to determine their efficacy in controlling bottom rot caused by R. solani on lettuce. Although in the first experiment all antagonists colonized the Rhizosphere of lettuce with CFU counts above 2 x 10(6) g(-1) of root fresh weight, only four isolates significantly reduced disease severity. In subsequent experiments involving these four antagonists, only Pseudomonas jessenii RU47 showed effective and consistent disease suppression. Plate counts and denaturing gradient gel electrophoresis (DGGE) fingerprints of Pseudomonas-specific gacA genes amplified from total community DNA confirmed that RU47 established as the dominant Pseudomonas population in the Rhizosphere of inoculated lettuce plants. Furthermore, the DGGE fingerprint revealed that R. solani AG1-IB inoculation severely affected the bacterial and fungal community structure in the Rhizosphere of lettuce and that these effects were much less pronounced in the presence of RU47. Although the exact mechanism of antagonistic activity and the ecology of RU47 remain to be further explored, our results suggest that RU47 is a promising agent to control bottom rot of lettuce.

Qirong Shen - One of the best experts on this subject based on the ideXlab platform.

  • RESEARCH ARTICLE Pectin Enhances Bio-Control Efficacy by Inducing Colonization and Secretion of Secondary Metabolites by Bacillus amyloliquefaciens SQY 162 in the Rhizosphere of Tobacco
    2016
    Co-Authors: Zhiying Fang, Rong Guo, Bin Pan, Wen Shi, Saifei Yuan, Huilin Guan, Ming Gong, Biao Shen, Qirong Shen
    Abstract:

    Bacillus amyloliquefaciens is a plant-beneficial Gram-positive bacterium involved in sup-pressing soil-borne pathogens through the secretion of secondary metabolites and high rhi-zosphere Competence. Biofilm formation is regarded as a prerequisite for high Rhizosphere Competence. In this work, we show that plant extracts affect the chemotaxis and biofilm for-mation of B. amyloliquefaciens SQY 162 (SQY 162). All carbohydrates tested induced the chemotaxis and biofilm formation of the SQY 162 strain; however, the bacterial growth rate was not influenced by the addition of carbohydrates. A strong chemotactic response and biofilm formation of SQY 162 were both induced by pectin through stimulation of surfactin synthesis and transcriptional expression of biofilm formation related matrix genes. These re-sults suggested that pectin might serve as an environmental factor in the stimulation of the biofilm formation of SQY 162. Furthermore, in pot experiments the surfactin production and the population of SQY 162 in the Rhizosphere significantly increased with the addition of su-crose or pectin, whereas the abundance of the bacterial pathogen Ralstonia decreased. With increased production of secondary metabolites in the Rhizosphere of tobacco by SQ

  • Pectin Enhances Bio-Control Efficacy by Inducing Colonization and Secretion of Secondary Metabolites by Bacillus amyloliquefaciens SQY 162 in the Rhizosphere of Tobacco
    PloS one, 2015
    Co-Authors: Zhiying Fang, Rong Guo, Bin Pan, Wen Shi, Saifei Yuan, Huilin Guan, Ming Gong, Biao Shen, Qirong Shen
    Abstract:

    Bacillus amyloliquefaciens is a plant-beneficial Gram-positive bacterium involved in suppressing soil-borne pathogens through the secretion of secondary metabolites and high Rhizosphere Competence. Biofilm formation is regarded as a prerequisite for high Rhizosphere Competence. In this work, we show that plant extracts affect the chemotaxis and biofilm formation of B. amyloliquefaciens SQY 162 (SQY 162). All carbohydrates tested induced the chemotaxis and biofilm formation of the SQY 162 strain; however, the bacterial growth rate was not influenced by the addition of carbohydrates. A strong chemotactic response and biofilm formation of SQY 162 were both induced by pectin through stimulation of surfactin synthesis and transcriptional expression of biofilm formation related matrix genes. These results suggested that pectin might serve as an environmental factor in the stimulation of the biofilm formation of SQY 162. Furthermore, in pot experiments the surfactin production and the population of SQY 162 in the Rhizosphere significantly increased with the addition of sucrose or pectin, whereas the abundance of the bacterial pathogen Ralstonia decreased. With increased production of secondary metabolites in the Rhizosphere of tobacco by SQY 162 and improved colonization density of SQY 162 in the pectin treatment, the disease incidences of bacterial wilt were efficiently suppressed. The present study revealed that certain plant extracts might serve as energy sources or environmental cues for SQY 162 to enhance the population density on tobacco root and bio-control efficacy of tobacco bacterial wilt.

Philippe Lemanceau - One of the best experts on this subject based on the ideXlab platform.

  • Identification of traits shared by Rhizosphere-competent strains of fluorescent pseudomonads.
    Microbial ecology, 2012
    Co-Authors: Sandrine Ghirardi, Fabrice Dessaint, Sylvie Mazurier, Thérèse Corberand, Jos M. Raaijmakers, Jean-marie Meyer, Yves Dessaux, Philippe Lemanceau
    Abstract:

    Rhizosphere Competence of fluorescent pseudomonads is a prerequisite for the expression of their beneficial effects on plant growth and health. To date, knowledge on bacterial traits involved in Rhizosphere Competence is fragmented and derived mostly from studies with model strains. Here, a population approach was taken by investigating a representative collection of 23 Pseudomonas species and strains from different origins for their ability to colonize the Rhizosphere of tomato plants grown in natural soil. Rhizosphere Competence of these strains was related to phenotypic traits including: (1) their carbon and energetic metabolism represented by the ability to use a wide range of organic compounds, as electron donors, and iron and nitrogen oxides, as electron acceptors, and (2) their ability to produce antibiotic compounds and N-acylhomoserine lactones (N-AHSL). All these data including origin of the strains (soil/Rhizosphere), taxonomic identification, phenotypic cluster based on catabolic profiles, nitrogen dissimilating ability, siderovars, susceptibility to iron starvation, antibiotic and N-AHSL production, and Rhizosphere Competence were submitted to multiple correspondence analyses. Colonization assays revealed a significant diversity in Rhizosphere Competence with survival rates ranging from approximately 0.1 % to 61 %. Multiple correspondence analyses indicated that Rhizosphere Competence was associated with siderophore-mediated iron acquisition, substrate utilization, and denitrification. However, the catabolic profile of one Rhizosphere-competent strain differed from the others and its Competence was associated with its ability to produce antibiotics phenazines and N-AHSL. Taken together, these data suggest that competitive strains have developed two types of strategies to survive in the Rhizosphere.

  • Identification of Traits Implicated in the Rhizosphere Competence of Fluorescent Pseudomonads: Description of a Strategy Based on Population and Model Strain Studies
    Sustainable Agriculture, 2009
    Co-Authors: Xavier Latour, Sandrine Delorme, Pascal Mirleau, Philippe Lemanceau
    Abstract:

    The lack of consistency of the beneficial effects of inoculated fluorescent pseudomonads has often been related to their bad survival in the Rhizosphere. In this review, we describe the strategy followed over the last decade to study traits involved in the Rhizosphere Competence of these bacteria. The diversity of indigenous populations associated with plant roots was first compared to that of populations associated with uncultivated soils in order to identify traits that discriminate these populations. The involvement of these bacterial traits in the Rhizosphere Competence was then assessed by comparing the competitiveness of a wild-type strain to that of mutants affected in the corresponding phenotypes. Finally, traits shared by populations adapted to the Rhizosphere were identified by comparing both the competitiveness in the Rhizosphere and the metabolism of a collection of bacterial strains. The data yielded indicated that Rhizosphere competent pseudomonads show a specific metabolism especially characterized by the efficiency of the pyoverdine-mediated iron uptake and by the ability to reduce nitrogen oxides.

  • Identification of traits implicated in the Rhizosphere Competence of fluorescent pseudomonads: description of a strategy based on population and model strain studies
    Agronomie, 2003
    Co-Authors: Xavier Latour, Sandrine Delorme, Pascal Mirleau, Philippe Lemanceau
    Abstract:

    International audienceThe lack of consistency of the beneficial effects of inoculated fluorescent pseudomonads has often been related to their bad survival in the Rhizosphere. In this review, we describe the strategy followed over the last decade to study traits involved in the Rhizosphere Competence of these bacteria. The diversity of indigenous populations associated with plant roots was first compared to that of populations associated with uncultivated soils in order to identify traits that discriminate these populations. The involvement of these bacterial traits in the Rhizosphere Competence was then assessed by comparing the competitiveness of a wild-type strain to that of mutants affected in the corresponding phenotypes. Finally, traits shared by populations adapted to the Rhizosphere were identified by comparing both the competitiveness in the Rhizosphere and the metabolism of a collection of bacterial strains. The data yielded indicated that Rhizosphere-competent pseudomonads show a specific metabolism especially characterized by the efficiency of the pyoverdine-mediated iron uptake and by the ability to reduce nitrogen oxides.Identification de caractères impliqués dans la compétence rhizosphérique des Pseudomonas spp. fluorescents : description d'une stratégie basée sur des études de populations et de souche modèle. Le manque de fiabilité des effets bénéfiques déterminés par les Pseudomonas spp. fluorescents inoculés a souvent été attribué à leur mauvaise survie dans la rhizosphère. Au cours de cette synthèse, nous décrivons la stratégie suivie lors des dix dernières années pour étudier les caractères impliqués dans la compétence rhizosphérique de ces bactéries. La diversité des populations indigènes associées aux racines a d'abord été comparée à celle des populations associées à des sols nus. L'implication de ces caractères bactériens dans la compétence rhizosphérique a ensuite été évaluée en comparant la compétitivité d'une souche modèle à celle de mutants affectés dans les phénotypes correspondants. Finalement, des caractères partagés par les populations adaptées à la rhizosphère ont été identifiés en comparant la compétitivité rhizosphérique et le métabolisme d'une collection de souches. Les données recueillies indiquent que les Pseudomonas spp. fluorescents adaptés à la rhizosphère présentent un métabolisme spécifique caractérisé, en particulier, par l'efficacité de leur système d'acquisition du fer basé sur les pyoverdines et par leur aptitude à réduire les oxydes d'azote