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Applied and Environmental Microbiology, July 1999, p. 3084-3094, Vol. 65, No. 7
Laboratoire de Microbiologie, I. R. D.,
Dakar, Sénégal1;
Laboratorium voor Microbiologie, Universiteit Gent, B-9000,
Ghent, Belgium2; and Laboratoire des
Symbioses Tropicales et Méditerranéennes, I. R. D.,
Campus de Baillarguet, 34032 Montpellier Cedex,
France3
Received 15 January 1999/Accepted 5 May 1999
We obtained nine bacterial isolates from root or collar nodules of
the non-stem-nodulated Aeschynomene species A. elaphroxylon, A. uniflora, or A. schimperi and 69 root or stem nodule isolates from the
stem-nodulated Aeschynomene species A. afraspera, A. ciliata, A. indica,
A. nilotica, A. sensitiva, and A. tambacoundensis from various places in Senegal. These
isolates, together with 45 previous isolates from various
Aeschynomene species, were studied for host-specific
nodulation within the genus Aeschynomene, also revisiting
cross-inoculation groups described previously by D. Alazard (Appl.
Environ. Microbiol. 50:732-734, 1985). The whole collection of
Aeschynomene nodule isolates was screened for synthesis of
photosynthetic pigments by spectrometry, high-pressure liquid chromatography, and thin-layer chromatography analyses. The presence of
puf genes in photosynthetic
Aeschynomene isolates was evidenced both by Southern
hybridization with a Rhodobacter capsulatus photosynthetic gene probe and by DNA amplification with primers defined from photosynthetic genes. In addition, amplified 16S ribosomal DNA restriction analysis was performed on 45 Aeschynomene
isolates, including strain BTAi1, and 19 reference strains from
Bradyrhizobium japonicum, Bradyrhizobium
elkanii, and other Bradyrhizobium sp. strains of uncertain taxonomic positions. The 16S rRNA gene sequence of
the photosynthetic strain ORS278 (LMG 12187) was determined and
compared to sequences from databases. Our main conclusion is that
photosynthetic Aeschynomene nodule isolates share the ability to nodulate particular stem-nodulated species and
form a separate subbranch on the Bradyrhizobium rRNA
lineage, distinct from B. japonicum and B. elkanii.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Photosynthetic Bradyrhizobia from Aeschynomene spp.
Are Specific to Stem-Nodulated Species and Form a Separate 16S
Ribosomal DNA Restriction Fragment Length Polymorphism
Group
*
Corresponding author. Mailing address: Laboratoire des
Symbioses Tropicales et Méditerranéennes, I.R.D., Campus de
Baillarguet, B.P. 5035, 34032 Montpellier Cedex, France. Phone:
(33) 04 67 59 38 24. Fax: (33) 4 67 59 38 02. E-mail:
P-De.Lajudie{at}mpl.ird.fr.
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