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Appl. Environ. Microbiol., May 1995, 1745-1749, Vol 61, No. 5
A Clays-Josserand, P Lemanceau, L Philippot and R Lensi
The distribution of nitrogen-dissimilative abilities among 317 isolates of
fluorescent pseudomonads was studied. These strains were isolated from an
uncultivated soil and from the rhizosphere, rhizoplane, and root tissue of
two plant species (flax and tomato) cultivated on this same soil. The
isolates were distributed into two species, Pseudomonas fluorescens (45.1%)
and Pseudomonas putida (40.4%), plus an intermediate type (14.5%). P.
fluorescens was the species with the greatest proportion of isolates in the
root compartments and the greatest proportion of dissimilatory and
denitrifying strains. According to their ability to dissimilate nitrogen,
the isolates have been distributed into nondissimilatory and dissimilatory
strains, nitrate reducers and true denitrifiers with or without N(inf2)O
reductase. The proportion of dissimilatory isolates was significantly
enhanced in the compartments affected by flax and tomato roots (55% in
uncultivated soil and 90 and 82% in the root tissue of flax and tomato,
respectively). Among these strains, the proportion of denitrifiers
gradually and significantly increased in the root vicinity of tomato (44,
68, 75, and 94% in uncultivated soil, rhizosphere, rhizoplane, and root
tissue, respectively) and was higher in the flax rhizoplane (66%) than in
the uncultivated soil. A higher proportion of N(inf2)O reducers was also
found in the root compartments. This result was particularly clear for
tomato. It is hypothesized that denitrification could be a selective
advantage for the denitrifiers in the root environment and that this
process could contribute to modify the specific composition of the
bacterial communities in the rhizosphere.
Copyright © 1995, American Society for Microbiology
Influence of Two Plant Species (Flax and Tomato) on the Distribution of Nitrogen Dissimilative Abilities within Fluorescent Pseudomonas spp
Laboratoire dEcologie Microbienne, Centre National de la Recherche Scientifique URA 1450, Universite Lyon I, 69622 Villeurbanne Cedex, and Laboratoire de Recherches sur la Flore Pathogene du Sol, Institut National de la Recherche Agronomique, 21034 Dijon Cedex, France
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