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Appl. Environ. Microbiol., May 1997, 1852-1860, Vol 63, No. 5
P Frey, P Frey-Klett, J Garbaye, O Berge and T Heulin
A collection of 300 isolates of fluorescent pseudomonads was established
from Douglas fir-Laccaria bicolor mycorrhizas and mycorrhizosphere and from
adjacent bulk soil. These isolates were first phenotypically characterized
with the Biolog method. Taxonomic identification assigned 90% of the
isolates to the different biovars of Pseudomonas fluorescens, with inverted
frequencies of biovars V and I from the bulk soil to the mycorrhizas,
suggesting that the mycorrhizas exert a selective stimulation of the P.
fluorescens bv. I and a counterselection of the P. fluorescens bv. V
present in the soil. Multivariate analyses of the carbon source utilization
data led to the definition of homogenous metabolic groups and to the
identification of the most discriminating substrates for each group. The
isolates from the mycorrhizosphere and from the mycorrhizas seem to
preferentially utilize carbohydrates, in particular trehalose, which is the
most abundant carbohydrate accumulated in the mycelium of L. bicolor. The
results suggest that L. bicolor exerts a trehalose-mediated selection on
the fluorescent pseudomonads present in the vicinity of the mycorrhizas.
Isolates of P. fluorescens from the mycorrhizosphere and mycorrhizas were
then genotypically characterized by restriction fragment length
polymorphism of PCR-amplified 16S rRNA genes and enterobacterial repetitive
intergenic consensus-PCR DNA fingerprinting. Both methods revealed a high
genetic polymorphism within the population studied, which was well
correlated with the phenotypic characterization.
Copyright © 1997, American Society for Microbiology
Metabolic and Genotypic Fingerprinting of Fluorescent Pseudomonads Associated with the Douglas Fir-Laccaria bicolor Mycorrhizosphere
Institut National de la Recherche Agronomique, Unite de Recherches Ecosystemes Forestiers, 54280 Champenoux, and Centre National de la Recherche Scientifique, Centre de Pedologie Biologique, UPR 6831 Associee a l'Universite H. Poincare Nancy I, 54501 Vandoeuvre-les-Nancy, France
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