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Applied and Environmental Microbiology, June 2001, p. 2790-2798, Vol. 67, No. 6
P. de Ecología Molecular y
Microbiana, Centro de Investigación sobre Fijación de
Nitrógeno, Universidad Nacional Autónoma de
México, Cuernavaca, Morelos, Mexico
Received 27 November 2000/Accepted 12 March 2001
The genus Burkholderia comprises 19 species, including
Burkholderia vietnamiensis which is the only known
N2-fixing species of this bacterial genus. The first
isolates of B. vietnamiensis were recovered from the
rhizosphere of rice plants grown in a phytotron, but its existence in
natural environments and its geographic distribution were not reported.
In the present study, most N2-fixing isolates recovered
from the environment of field-grown maize and coffee plants cultivated
in widely separated regions of Mexico were phenotypically identified as
B. cepacia using the API 20NE system. Nevertheless, a
number of these isolates recovered from inside of maize roots, as well
as from the rhizosphere and rhizoplane of maize and coffee plants,
showed similar or identical features to those of B. vietnamiensis TVV75T. These features include
nitrogenase activity with 10 different carbon sources, identical or
very similar nifHDK hybridization patterns, very similar
protein electrophoregrams, identical amplified 16S rDNA restriction
(ARDRA) profiles, and levels of DNA-DNA reassociation higher than 70%
with total DNA from strain TVV75T. Although the ability to
fix N2 is not reported to be a common feature among the
known species of the genus Burkholderia, the results
obtained show that many diazotrophic Burkholderia isolates analyzed showed phenotypic and genotypic features different from those
of the known N2-fixing species B. vietnamiensis
as well as from those of B. kururiensis, a bacterium
identified in the present study as a diazotrophic species.
DNA-DNA reassociation assays confirmed the existence of
N2-fixing Burkholderia species different from
B. vietnamiensis. In addition, this study shows the wide
geographic distribution and substantial capability of N2-fixing Burkholderia spp. for colonizing
diverse host plants in distantly separated environments.
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.6.2790-2798.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Burkholderia, a Genus Rich in
Plant-Associated Nitrogen Fixers with Wide Environmental and
Geographic Distribution
*
Corresponding author. Mailing address: Centro de
Investigación sobre Fijación de Nitrógeno, UNAM, Ap.
Postal No. 565-A, Cuernavaca, Morelos, Mexico. Fax: (73) 17-55-81. E-mail: jesuscab{at}cifn.unam.mx.
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