Effects of Pseudomonas fluorescens F113 on Ecological Functions in the Pea Rhizosphere Are Dependent on pH

Naseby, D.C.; Lynch, J. M.

doi:10.1007/s002489900147

Cited by 33 publications

(21 citation statements)

References 24 publications

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“…Pseudomonas fluorescens F113, which was originally isolated from sugar beet rhizosphere (Shanahan et al 1992), is an excellent coloniser of several plant rhizospheres, such as those of sugar beet (Shanahan et al 1992, Delany et al 2001, tomato (Simons et al 1996), pea (Naseby and Lynch 1999), alfalfa (Villacieros et al 2003) and willow (Karlson, unpublished results). Derivatives of strain F113 with rhizoremediation ability were constructed genetically.…”

Section: Introductionmentioning

confidence: 99%

Degradation of PCB congeners by bacterial strains

Rein

Fernqvist

Mayer

et al. 2007

Appl Microbiol Biotechnol

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Biological in situ methods are options for the remediation of contaminated sites. An approach to quantify biodegradation by soil bacteria was developed, combining experiment with mathematical modelling. We performed in vitro assays to investigate the potential and kinetics of the wild-type degrader, Burkholderia sp. strain LB400 (expressing bph) and the genetically modified Pseudomonas fluorescens strains F113pcb and F113L::1180 (expressing bph under different promoters) to metabolise individual congeners of polychlorinated biphenyls (PCBs). Kinetics of metabolism was analysed using the Monod model.Results revealed similar patterns of degradable PCB congeners for LB400 and F113L::1180. The degree of PCB degradation was comparable for LB400 and F113L::1180, but was much lower for F113rifpcb. In additional mesocosm experiments with PCB contaminated soil, the F113 derivatives demonstrated a good survival ability in willow (Salix sp.) rhizosphere.Strain F113L::1180 in combination with willow plants is expected to degrade a large spectrum of PCB congeners in soil. The data from the experiments were used to calculate the time scale of the degradation process in a PCB-contaminated soil. The uncertainty of the model predictions due to the uncertainties of experimental removal velocities and bacterial cell density in soil was quantified.

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Section: Introductionmentioning

confidence: 99%

Degradation of PCB congeners by bacterial strains

Rein

Fernqvist

Mayer

et al. 2007

Appl Microbiol Biotechnol

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“…This strain, which is able to efficiently colonize the rhizosphere of a variety of plants (12,14,27,33), is being used as a model for rhizosphere colonization (3,26,33) and has also been genetically modified for polychlorinated biphenyl (PCB) rhizoremediation (5, 13, 41). The biocontrol ability of this strain has been related to the production of a series of secondary metabolites, including siderophores, diacetyl-phloroglucinol (DAPG), hydrogen cyanide, and an extracellular protease (1, 36), whose production is regulated by the GacAS posttranscriptional system (1).…”

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Pseudomonas fluorescens F113 Mutant with Enhanced Competitive Colonization Ability and Improved Biocontrol Activity against Fungal Root Pathogens

Barahona

Navazo

Martínez‐Granero

et al. 2011

Appl Environ Microbiol

122

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Motility is one of the most important traits for efficient rhizosphere colonization by Pseudomonas fluorescens F113rif (F113). In this bacterium, motility is a polygenic trait that is repressed by at least three independent pathways, including the Gac posttranscriptional system, the Wsp chemotaxis-like pathway, and the SadB pathway. Here we show that the kinB gene, which encodes a signal transduction protein that together with AlgB has been implicated in alginate production, participates in swimming motility repression through the Gac pathway, acting downstream of the GacAS two-component system. Gac mutants are impaired in secondary metabolite production and are unsuitable as biocontrol agents. However, the kinB mutant and a triple mutant affected in kinB, sadB, and wspR (KSW) possess a wild-type phenotype for secondary metabolism. The KSW strain is hypermotile and more competitive for rhizosphere colonization than the wild-type strain. We have compared the biocontrol activity of KSW with those of the wild-type strain and a phenotypic variant (F113v35 [V35]) which is hypermotile and hypercompetitive but is affected in secondary metabolism since it harbors a gacS mutation. Biocontrol experiments in the Fusarium oxysporum f. sp. radicis-lycopersici/Lycopersicum esculentum (tomato) and Phytophthora cactorum/Fragaria vesca (strawberry) pathosystems have shown that the three strains possess biocontrol activity. Biocontrol activity was consistently lower for V35, indicating that the production of secondary metabolites was the most important trait for biocontrol. Strain KSW showed improved biocontrol compared with the wild-type strain, indicating that an increase in competitive colonization ability resulted in improved biocontrol and that the rational design of biocontrol agents by mutation is feasible.Pseudomonas fluorescens F113rif (F113) is a biocontrol agent isolated from the sugar beet rhizosphere (36) that is able to suppress take-all disease produced by the oomycete Pythium ultimum (18). This strain, which is able to efficiently colonize the rhizosphere of a variety of plants (12,14,27,33), is being used as a model for rhizosphere colonization (3,26,33) and has also been genetically modified for polychlorinated biphenyl (PCB) rhizoremediation (5, 13, 41). The biocontrol ability of this strain has been related to the production of a series of secondary metabolites, including siderophores, diacetyl-phloroglucinol (DAPG), hydrogen cyanide, and an extracellular protease (1, 36), whose production is regulated by the GacAS posttranscriptional system (1).The GacAS system, as well as SadB and the Wsp system, independently regulates swimming motility in strain F113 (29). In this strain mutants affected in sadB and wspR showed increased swimming motility. In F113, the sadB and wspR genes showed 84% and 83% identities with their Pseudomonas aeruginosa orthologues and are highly conserved in sequence and genomic context with orthologues in all the sequenced P. fluorescens strains. SadB and WspR possibly repress swimming mot...

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“…strain LB400 bph operon under the control of different regulatory elements (4,38). P. fluorescens F113 is a good rhizosphere colonizer and can colonize the rhizospheres of different plants such as alfalfa (37), tomato (33), and pea (23).…”

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Rhizosphere Selection of Highly Motile Phenotypic Variants of Pseudomonas fluorescens with Enhanced Competitive Colonization Ability

Martínez‐Granero

Rivilla

Martín

2006

Appl Environ Microbiol

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Phenotypic variants of Pseudomonas fluorescens F113 showing a translucent and diffuse colony morphologyshow enhanced colonization of the alfalfa rhizosphere. We have previously shown that in the biocontrol agent P. fluorescens F113, phenotypic variation is mediated by the activity of two site-specific recombinases, Sss and XerD. By overexpressing the genes encoding either of the recombinases, we have now generated a large number of variants (mutants) after selection either by prolonged laboratory cultivation or by rhizosphere passage. All the isolated variants were more motile than the wild-type strain and appear to contain mutations in the gacA and/or gacS gene. By disrupting these genes and complementation analysis, we have observed that the Gac system regulates swimming motility by a repression pathway. Variants isolated after selection by prolonged cultivation formed a single population with a swimming motility that was equal to the motility of gac mutants, being 150% more motile than the wild type. The motility phenotype of these variants was complemented by the cloned gac genes. Variants isolated after rhizosphere selection belonged to two different populations: one identical to the population isolated after prolonged cultivation and the other comprising variants that besides a gac mutation harbored additional mutations conferring higher motility. Our results show that gac mutations are selected both in the stationary phase and during rhizosphere colonization. The enhanced motility phenotype is in turn selected during rhizosphere colonization. Several of these highly motile variants were more competitive than the wild-type strain, displacing it from the root tip within 2 weeks.Pseudomonas fluorescens F113 is a biocontrol agent isolated from the sugar beet rhizosphere (11) and capable of protecting this crop against the pathogenic fungus Pythium ultimum (17,31). In addition, derivatives of this strain with the ability to degrade polychlorinated biphenyls have been constructed by the integration of the Burkholderia sp. strain LB400 bph operon under the control of different regulatory elements (4, 38). P. fluorescens F113 is a good rhizosphere colonizer and can colonize the rhizospheres of different plants such as alfalfa (37), tomato (33), and pea (23).During alfalfa rhizosphere colonization, F113 undergoes phenotypic variation (27) characterized by the appearance of variants with a translucent and diffuse colony morphology. These variants were more prevalent in distal parts of the root (1, 27). Phenotypic variation in this strain appears to be mediated by the activity of two site-specific recombinases, Sss and XerD, since mutants with mutations in either of the genes encoding these recombinases show a severe reduction in the appearance of phenotypic variants after rhizosphere colonization and prolonged laboratory cultivation (22). Phenotypic variation seems to be an important trait for rhizosphere colonization, and mutants of different Pseudomonas strains affected in the sss (10, 22) or xerD (22) genes are ...

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Effects of Pseudomonas fluorescens F113 on Ecological Functions in the Pea Rhizosphere Are Dependent on pH

Cited by 33 publications

References 24 publications

Degradation of PCB congeners by bacterial strains

Degradation of PCB congeners by bacterial strains

Pseudomonas fluorescens F113 Mutant with Enhanced Competitive Colonization Ability and Improved Biocontrol Activity against Fungal Root Pathogens

Rhizosphere Selection of Highly Motile Phenotypic Variants of Pseudomonas fluorescens with Enhanced Competitive Colonization Ability

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