0000000000372700
AUTHOR
Jean-marie Meyer
Fitness in soil and rhizosphere of Pseudomonas fluorescens C7R12 compared with a C7R12 mutant affected in pyoverdine synthesis and uptake.
International audience; Fluorescent pseudomonads have evolved an efficient strategy of iron uptake based on the synthesis of the siderophore pyoverdine and its relevant outer membrane receptor. The possible implication of pyoverdine synthesis and uptake on the ecological competence of a model strain (Pseudomonas fluorescens C7R12) in soil habitats was evaluated using a pyoverdine minus mutant (PL1) obtained by random insertion of the transposon Tn5. The Tn5 flanking DNA was amplified by inverse PCR and sequenced. The nucleotide sequence was found to show a high level of identity with pvsB, a pyoverdine synthetase. As expected, the mutant PL1 was significantly more susceptible to iron starva…
Diversity of root-associated fluorescent pseudomonads as affected by ferritin overexpression in tobacco
A transgenic tobacco overexpressing ferritin (P6) was recently shown to accumulate more iron than the wild type (WT), leading to a reduced availability of iron in the rhizosphere and shifts in the pseudomonad community. The impact of the transgenic line on the community of fluorescent pseudomonads was assessed. The diversity of 635 isolates from rhizosphere soils, rhizoplane + root tissues, and root tissues of WT and P6, and that of 98 isolates from uncultivated soil was characterized. Their ability to grow under iron stress conditions was assessed by identifying their minimal inhibitory concentrations of 8-hydroxyquinoline for each isolate, pyoverdine diversity by isoelectrofocusing and ge…
Siderophore typing, a powerful tool for the identification of fluorescent and nonfluorescent Pseudomonas
ABSTRACT A total of 301 strains of fluorescent pseudomonads previously characterized by conventional phenotypic and/or genomic taxonomic methods were analyzed through siderotyping, i.e., by the isoelectrophoretic characterization of their main siderophores and pyoverdines and determination of the pyoverdine-mediated iron uptake specificity of the strains. As a general rule, strains within a well-circumscribed taxonomic group, namely the species Pseudomonas brassicacearum , Pseudomonas fuscovaginae , Pseudomonas jessenii , Pseudomonas mandelii , Pseudomonas monteilii , “ Pseudomonas mosselii ,” “ Pseudomonas palleronii ,” Pseudomonas rhodesiae , “ Pseudomonas salomonii ,” Pseudomonas syringa…
Pseudomonas salomonii sp. nov., pathogenic on garlic, and Pseudomonas palleroniara sp. nov., isolated from rice
International audience; A total of 26 strains, including 15 strains isolated from garlic plants with the typical symptoms of 'Café au lait' disease and 11 strains isolated from diseased or healthy rice seeds and sheaths infested by Pseudomonas fuscovaginae, were compared with 70 type or reference strains of oxidase-positive pathogenic or non-pathogenic fluorescent pseudomonads. The strains were characterized by using a polyphasic taxonomic approach. Numerical taxonomy of phenotypic characteristics showed that the garlic and rice strains were related to each other. However, they clustered into separate phenons, distinct from those of the other strains tested, and were different in several nu…
Pseudomonas lini sp. nov., a novel species from bulk and rhizospheric soils.
The taxonomic position of eight fluorescent Pseudomonas strains isolated from bulk and rhizospheric soils, and from water was examined. These eight strains clustered in one phenon together with Pseudomomas mandelii (CFBP 4844T), but could still be differentiated from this type strain by four phenotypic features. The eight stains exhibited internal DNA-DNA hybridization values ranging from 60 to 100%, with deltaTm below 5 degrees C (3.9 and 4.3 degrees C) for the lowest values (60 and 66%). The percentages of hybridization with type or reference strains of other Pseudomonas species tested ranged from 12 to 60% (deltaTm = 5.5 degrees C), indicating that the eight isolates studied constituted …
Chapter 4 Iron Dynamics in the Rhizosphere
Abstract Iron is an essential micronutrient for most organisms due to its role in fundamental metabolic processes. In cultivated soils, soil solution iron is mostly oxidized [Fe(III) species] unless local anoxic conditions develop. The concentration of these Fe(III) species is small in soil solution due to the low solubility of ferric oxides, oxyhydroxides, and hydroxides, which is minimal at neutral and alkaline pH. In the rhizosphere, iron concentration in the soil solution is even lower because of its uptake by aerobic organisms (plants and microorganisms), leading to a high level of competition for Fe(III). In order to face iron competition, these organisms have evolved active uptake st…