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Applied and Environmental Microbiology, May 2001, p. 2255-2262, Vol. 67, No. 5
UMR CNRS 5557 Ecologie Microbienne,
Université Claude Bernard Lyon 1, 69622 Villeurbanne Cedex,
France
Received 27 October 2000/Accepted 18 February 2001
The similarities and differences in the structures of the
nifH gene pools of six different soils (Montrond,
LCSA-p, Vernon, Dombes, LCSA-c, and Thysse Kaymor) and five soil
fractions extracted from LCSA-c were studied. Bacterial DNA was
directly extracted from the soils, and a region of the
nifH gene was amplified by PCR and analyzed by
restriction. Soils were selected on the basis of differences in soil
management, plant cover, and major physicochemical properties.
Microenvironments differed on the basis of the sizes of the constituent
particles and the organic carbon and clay contents. Restriction
profiles were subjected to principal-component analysis. We showed that
the composition of the diazotrophic communities varied both on a large
scale (among soils) and on a microscale (among microenvironments in
LCSA-c soil). Soil management seemed to be the major parameter
influencing differences in the nifH gene pool structure
among soils by controlling inorganic nitrogen content and its
variation. However, physicochemical parameters (texture and total C and
N contents) were found to correlate with differences among
nifH gene pools on a microscale. We hypothesize that the
observed nifH genetic structures resulted from the
adaptation to fluctuating conditions (cultivated soil, forest soil,
coarse fractions) or constant conditions (permanent pasture soil, fine fractions). We attempted to identify a specific band within the profile
of the clay fraction by cloning and sequencing it and comparing it with
the gene databases. Unexpectedly, the nifH sequences of
the dominant bacteria were most similar to sequences of unidentified marine eubacteria.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.5.2255-2262.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Comparison of nifH
Gene Pools in Soils and Soil Microenvironments with Contrasting
Properties
*
Corresponding author. Mailing address: UMR CNRS 5557 Ecologie Microbienne, Bat. 741/4, Université Claude Bernard Lyon
1, 43 Bd. 11 Novembre 1918, 69622 Villeurbanne Cedex, France. Phone: 33 04 72 43 13 24. Fax: 33 04 72 43 12 23. E-mail:
poly{at}biomserv.univ-lyon1.fr.
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