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Legume Symbiotic Nitrogen Fixation by ß-Proteobacteria Is Widespread in Nature

Wen-Ming Chen,¹ Lionel Moulin,^2, Cyril Bontemps,^2,3 Peter Vandamme,⁴ Gilles Béna,² and Catherine Boivin-Masson^2,3*

Laboratory of Microbiology, Department of Seafood Science, National Kaohsiung Institute of Marine Technology, Kaohsiung City 811, Taiwan,¹ LSTM, IRD-INRA-CIRAD-ENSAM, TA 10/J, Baillarguet, 34 398 Montpellier Cedex 5,² Laboratoire des Interactions Plantes Micro-Organismes, INRA-CNRS, 31 326 Castanet-Tolosan Cedex, France,³ Laboratorium voor Microbiologie, Universiteit Gent, B-9000 Ghent, Belgium⁴

Received 20 June 2003/ Accepted 24 September 2003

	ABSTRACT

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Following the initial discovery of two legume-nodulating Burkholderia strains (L. Moulin, A. Munive, B. Dreyfus, and C. Boivin-Masson, Nature 411:948-950, 2001), we identified as nitrogen-fixing legume symbionts at least 50 different strains of Burkholderia caribensis and Ralstonia taiwanensis, all belonging to the ß-subclass of proteobacteria, thus extending the phylogenetic diversity of the rhizobia. R. taiwanensis was found to represent 93% of the Mimosa isolates in Taiwan, indicating that ß-proteobacteria can be the specific symbionts of a legume. The nod genes of rhizobial ß-proteobacteria (ß-rhizobia) are very similar to those of rhizobia from the -subclass (-rhizobia), strongly supporting the hypothesis of the unique origin of common nod genes. The ß-rhizobial nod genes are located on a 0.5-Mb plasmid, together with the nifH gene, in R. taiwanensis and Burkholderia phymatum. Phylogenetic analysis of available nodA gene sequences clustered ß-rhizobial sequences in two nodA lineages intertwined with -rhizobial sequences. On the other hand, the ß-rhizobia were grouped with free-living nitrogen-fixing ß-proteobacteria on the basis of the nifH phylogenetic tree. These findings suggest that ß-rhizobia evolved from diazotrophs through multiple lateral nod gene transfers.

	INTRODUCTION

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Members of the Leguminosae, comprising about 18,000 species, play an important ecological role, with representatives in nearly every type of plant on Earth. Most species are able to form nitrogen-fixing symbioses with specific bacteria known as rhizobia. The recent identification of two ß-proteobacterial strains of the genus Burkholderia able to nodulate legumes (10) changed the long-held dogma that only bacteria of the subdivision are able to nodulate legumes (18, 23). These two strains were subsequently described as Burkholderia tuberum and Burkholderia phymatum (24). In addition, eight strains isolated from root nodules of Mimosa spp. were recently described as Ralstonia taiwanensis, also classified as ß-proteobacteria (1), although their nodulation capacity was not confirmed. The terms - and ß-rhizobia were proposed to distinguish the rhizobial - and ß-proteobacteria, respectively (10). This unexpected discovery raised the question as to whether nodulation by ß-proteobacteria is an extremely rare phenomenon or whether it had simply been overlooked until now. Moreover, the fact that the first two nodulating Burkholderia strains were isolated from Aspalathus and Machaerium spp., which are known to be associated with Bradyrhizobium (2, 12), may suggest that these ß-proteobacteria are not the specific partners of the respective host legumes.

In this article, we confirm the widespread phylogenetic diversity of nitrogen-fixing legume symbionts by identifying as ß-rhizobia an additional 2 Burkholderia strains from the species Burkholderia caribensis and a collection of at least 44 R. taiwanensis strains. These data increase to four the number of different ß-rhizobial species identified so far, originating from three different continents. Moreover, we show that R. taiwanensis is the preferred partner of Mimosa pudica and Mimosa diplotricha in Taiwan. ß-Rhizobia possess nod and nif genes which are very similar to those of -rhizobia and which are located on a symbiotic plasmid. Phylogenetic analysis of available nodA and nifH genes from - and ß-proteobacteria suggests that ß-rhizobia have evolved from diazotrophs through multiple lateral gene transfers.

	MATERIALS AND METHODS

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Bacterial strains and growth conditions. The Mimosa strains used in these studies are listed in Table 1. B. phymatum STM815, isolated from Machaerium lunatum in French Guiana, was previously described (10, 24). Mimosa strains were isolated from root nodules collected at 14 sites in Taiwan (Fig. 1) by using a previously described isolation procedure (1). Strains were maintained and grown on yeast extract-mannitol medium (18) at 28°C.

View larger version (18K): [in this window] [in a new window]   FIG. 1. Sampling sites for M. pudica and M. diplotricha in Taiwan.

Nearly full-length 16S ribosomal DNA (rDNA) was amplified and sequenced as previously described (1). 16S rDNA PCR-restriction fragment length polymorphism (RFLP) analysis was performed as described previously (1), except that AluI, CfoI, HinfI, and MspI were used. nodA amplification and sequencing were performed with pairs of primers with the sequences 5'-TGGARVBTNYSYTGGGAAA-3' and5'-TCAYARYTCNGRNCCRTTYC-3' (strains LMG 19424, LMG 19425, TJ171, and TJ182), 5'-TGGARVBTNYSYTGGGAAA-3' and 5'-GGRTKNGGNCCRTCRTCRAANGT-3' (strains TJ167, TJ172, and TJ173), and 5'-TGCRGTGGAARNTRBVYTGGGAAA-3' and 5'-TCACARCTCKGGCCCGTTCCG-3' (strain STM815). nodA PCR-RFLP analysis was performed with a 531-bp PCR product obtained with a primer pair with the sequences 5'-ATCTTGAACTCTCCGACC-3' and 5'-GTTCGATTGTTTCGCCG-3' and digested with AluI, CfoI, HinfI, MspI, and NdeII.

A 520-bp fragment containing part of the nodH and nodA genes of strain LMG 19424 was amplified and sequenced with primers with the sequences 5'-GCCATCCACATCATCGATG-3' and 5'-CGGCTTCGCATTGAAAGGC-3'. A 2.1-kb fragment containing the nodB gene and part of the nodC gene of strain LMG 19424 was amplified with primers with the sequences 5'-CAGATCNAGDCCBTTGAARCGCA-3' and 5'-CTNCGNGCCCARCGNAGTTG-3'. A 1.2-kb overlapping fragment containing part of the nodC and nodI genes was amplified with primers with the sequences 5'-GTATGTTCCTAACGCTATCGCGGC-3' and 5'-TCTTCCATVAWRTGVGTNGTCA-3'. These fragments were further sequenced with pairs of degenerate primers based on available nodB, nodC, and nodI alignments.

A 640-bp fragment containing part of the nifH gene was amplified and sequenced with primers with the sequences 5'-CGCIWTYTACGGIAARGGIGG-3' and 5'-GGIKCRTAYTSGATIACIGTCAT-3'.

PCR products of 440 to 636 bp, used as probes for PFGE hybridization, were amplified from LMG 19424 and STM815 with primer pairs with the sequences 5'-AARGGNGGNATYGGHAARTC-3' and 5'-GCRTAVAKNGCCATCATYTC-3' (for nifH), 5'-GGTTCCACGTAAGCTTCCCTCWCCGAYCAYWTSGARTTGGC-3' and 5'-GCGATTACCCTGTACACCCACAGSTYKGGYCCCCGTTCCG-3' (for nodA), and 5'-GGTTCCACGTAAGCTTCCCGACATGGAGTACTGGCTCGC-3') and 5'-GCGATTACCCTGTACACCCGACAGCCAATCGCTATTTCCG-3' (for nodC).

Phylogenetic analysis. Multiple alignments were performed with CLUSTAL X (19) and manually corrected by using GeneDoc (11). Phylogenetic analysis was carried out with a maximum-likelihood (ML) approach by using PAUP version 4.0b10 (17). Two types of substitution (the substitution matrix being estimated by ML), three classes of site rate variation based on the codon structure of the DNA sequence, and base frequencies were estimated from the data by the ML approach. The same model was applied for both nifH and nodA phylogenies. Node robustness was esimated by bootstrap analysis by combining the Seqboot and DnaML programs from the PHYLIP package (5).

Plant tests. Seeds were surface sterilized with concentrated sulfuric acid for 10 min and then with 3% sodium hyperchlorite for 10 min. Plant cultivation and nodulation tests were carried out as described previously (8). Nitrogen fixation was estimated by visual observation of the vigor and foliage color of 60-day-old plants. Fresh nodules were observed under an Olympus SHZ 10 stereomicroscope. Sections 80 µm thick were prepared by using a Leica VT1000S Vibratome. Microscopic preparations were cleared with sodium hypochlorite and stained with methylene blue as described by Truchet et al. (21).

Nucleotide sequence accession numbers. EMBL accession numbers for the 16S rRNA genes are as follows: AJ505296 (TJ167), AJ505297 (TJ170), AJ505298 (TJ171), AJ505299 (TJ172), AJ505300 (TJ173), and AJ505301(TJ182). Accession numbers for the nifH genes are as follows: AJ505312 (TJ173), AJ505313 (TJ172), AJ505314 (TJ171), AJ505315 (TJ170), AJ505316 (TJ167), AJ505317 (TJ182), AJ505319 (STM815), AJ505320 (LMG 19424), and AJ505321 (LMG 19425). Accession numbers for the nodA genes are as follows: AJ505304 (LMG 19425), AJ505305 (TJ167), AJ505306 (TJ171), AJ505307 (TJ172), AJ505308 (TJ173), AJ505309 (TJ182), AJ55310 (STM1441), AJ505311 (LMG 19424), and AJ505318 (STM815). The accession number for nodBCI of LMG 19424 is AJ505303.

	RESULTS

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Most rhizobia isolated from M. pudica and M. diplotricha in Taiwan belong to the genus Ralstonia. To further examine the taxonomic diversity of Mimosa nodule isolates, 190 new isolates were recovered from root nodules of M. pudica and M. diplotricha plants growing in 14 different areas in Taiwan (Table 1).

16S rDNA PCR-RFLP analysis grouped 177 isolates together with R. taiwanensis reference strains (Table 1). Additional PFGE and nodA PCR-RFLP (see below) analyses showed that these R. taiwanensis isolates represented at least 44 different strains (Table 1). The remaining 13 isolates fell into six PFGE pattern groups. 16S rDNA sequencing of representative strains of these groups showed that they belonged to the genus Burkholderia (strains TJ182 and TJ183) (Fig. 2), the genus Rhizobium (TJ167 to TJ169, TJ171 to TJ176, and TJ189) (data not shown), or the genus Sinorhizobium (TJ170) (data not shown) (Table 1). Further taxonomical analysis identified TJ182 and TJ183 as B. caribensis (24) (Fig. 2).

View larger version (32K): [in this window] [in a new window]   FIG. 2. 16S rDNA tree showing phylogenetic positions of legume-nodulating Ralstonia and Burkholderia species within the ß-proteobacteria. The ML tree (base frequencies estimated, mutation rates drawn from an + INVdistribution, four classes of mutations) was reconstructed by using PAUP. Xanthomonas campestris was used as an outgroup. Legume symbionts are shown in bold type. Nodulating Burkholderia strains are named according to Vandamme et al. (24). GenBank/EMBL accession numbers for the 16S rDNA sequences were AF175314 (B. cepacia genomovar VI), AF148556 (B. cepacia genomovar III), U96928 (B. vietnamensis), U91839 (B. pseudomallei), AF110188 (B. mallei), AB021423 (B. carophylli), AJ302312 (B. phymatum), AJ505301 (B. caribensis), Y17009 (B. caribensis), AF215705 (B. fungorum), AB021394 (B. phenazinium), U96939 (B. graminis), AB024310 (B. kuruiensis), AJ302311 (B. tuberum), AF139176 (P. sputorum), AF139176 (G. gigasporum), AJ238359 (H. frisingense), AL646072 (R. solanacearum), AB004790 (R. pickettii),AF085226 (R. paucula), AF300324 (R. taiwanensis), AF076645 (R. gilardii), M32021 (R. eutropha), and AF188831 (X. campestris).

View larger version (143K): [in this window] [in a new window]   FIG. 3. Nodules of M. pudica 4 weeks after inoculation with R. taiwanensis LMG 19424. (a) Nodulated roots. (b) Root segment with pink nodules. (c) Longitudinal section showing the structure of a nodule. Plant tissue was cleared with sodium hypochlorite and stained with methylene blue as described by Truchet et al. (21). ic, infected cells; vb, vascular bundles.

Ralstonia and Burkholderia nod and nif genes are very similar to those of -rhizobia.

Part of the nifH gene, encoding dinitrogenase reductase, a key enzyme in nitrogen fixation, was also amplified and sequenced in representative strains of R. taiwanensis, B. caribensis, B. phymatum, and Rhizobium spp. (data not shown).

nod and nif genes are located on a plasmid in R. taiwanensis and B. phymatum. Genes required for nodulation and symbiotic nitrogen fixation are often clustered and located on large plasmids (9) or mobile symbiotic islands (15). To determine the locations of symbiotic genes in the genomes of the new ß-rhizobia, we first examined the genome organization of Ralstonia and Burkholderia representatives by using PFGE (Fig. 4). Two high-molecular-weight replicons with apparent sizes of 3.5 and 2.4 Mb and a smaller replicon of about 0.5 Mb were identified for R. taiwanensis LMG 19424, while B. phymatum STM815 possesses replicons of approximately 3.5, 2.8, 2.1, and 0.5 Mb. No readable PFGE profile could be obtained with B. tuberum. To determine which replicons carry the symbiotic genes, Southern blots of PFGE agarose gels were hybridized with nifH and either nodA or nodC probes. Both nod and nif probes hybridized with the smallest 0.5-Mb replicons of R. taiwanensis and B. phymatum (Fig. 4). These symbiotic replicons did not hybridize with parental strain 16S rRNA, suggesting that they are genuine plasmids (data not shown).

View larger version (80K): [in this window] [in a new window]   FIG. 4. Locations of nodA and nifH genes on replicons of R. taiwanensis LMG 19424 (A) and B. phymatum STM815 (B). Lane 1, PFGE of undigested genomic DNA stained with ethidium bromide; lanes 2 and 3, autoradiographs of blotted PFGE gels hybridized with nodA and nifH probes, respectively. Sizes of replicons are indicated on the left.

Phylogenetic analysis of nodA and nifH genes of - and ß-rhizobia. Phylogenetic analysis of 42 nodA sequences—including most available -rhizobial and four ß-rhizobial sequences—resulted in the ML tree shown in Fig. 5. The four ß-proteobacteria fell into two strongly supported clades. B. phymatum, B. caribensis, and R. taiwanensis strains clustered in the same clade. The nodA sequence closest to this clade comes from the highly divergent and atypical A. caulinodans, although this finding may have resulted from a long branch attraction artifact (4). B. tuberum and Methylobacterium nodulans fell into a separate and strongly supported cluster. Interestingly, the ß-rhizobia R. taiwanensis and B. caribensis and the -rhizobia Rhizobium sp. strains TJ167 and TJ172 isolated from M. diplotricha clustered separately in the nodA tree, suggesting that their nodulation genes have different origins.

View larger version (34K): [in this window] [in a new window]   FIG. 5. Unrooted nodA phylogenetic tree of rhizobia. ß-Proteobacterial strains are in shown in bold type and underlined. The tree was reconstructed by using an ML approach based on a 597-bp alignment (excluding the additional segment at the N-terminal part). Sequence lengths included ranged from 558 bp (B. phymatum STM815; partial sequence) to 597 bp (most strains). Values along branches indicate bootstrap percentages higher than 50%, based on 100 replicates. nodA sequences for published bacteria are available from GenBank. EMBL accession numbers and nodA sequences for unpublished bacteria were AJ505318 (B. phymatum), AJ505311 (R. taiwanensis), AJ505309 (B. caribensis), AJ300229 (S. terangae bv. acaciae), AJ300249 (M. plurifarium), AJ505307 (TJ172), AJ300234 (BR816), AJ505305 (TJ167), AJ300242 (A. undicola), AJ302321 (B. tuberum), AJ303088 (STM259), AJ430707 (WU425), AJ430730 (CBP70), AJ430715 (ORS938), AJ430712 (USDA3139), AJ430728 (CCT6220), AJ300260 (STM270), AJ300247 (M. ciceri), AJ300228 (S. terangae bv. sesbaniae), and J300235 (R. huautlense).

Interestingly, the phylogeny of the nitrogen fixation gene nifH provides a representation of the rhizobia different from that of the phylogeny of nodA (Fig. 6). Indeed, some of the groupings within the nifH tree corresponded to the phylogeny of the organisms as deduced from comparative 16S rDNA analysis, although - and ß-proteobacteria did not form distinct and monophyletic clades. Moreover, the nifH tree grouped together free-living and symbiotic nitrogen-fixing Burkholderia and Ralstonia strains. An example of a representative organism is B. tuberum, which grouped with M. nodulans in the nodA phylogeny but grouped with other ß-proteobacteria in the nifH phylogeny. Constraining either -and ß-rhizobia or M. nodulans and B. tuberum to the same clade led to a tree that was statistically less probable than the ML tree (both with P values of <10^-4). These results suggest that nod and nif genes of ß-rhizobia have different origins.

View larger version (66K): [in this window] [in a new window]   FIG. 6. nifH phylogenetic tree. The tree was reconstructed by using an ML approach based on an 800-bp alignment matrix (partial and full sequence lengths ranged from 336 to 797 bp). Values along branches indicate bootstrap percentages higher than 50%. The tree was rooted by using sequences from V. diazotrophicus, K. pneumoniae, and A. vinelandii. Rhizobia are shown in bold type, and the -, ß-, or -proteobacterial classification is indicated in parentheses. Clusters 1 and 3 contain -rhizobia only, while cluster 2 includes both symbiotic and nonsymbiotic diazotrophic ß-proteobacteria. nifH sequences for published bacteria are available from GenBank EMBL. EMBL accession numbers and nifH sequences for unpublished bacteria were AJ302315 (B. tuberum), AJ505320 (R. taiwanensis), AJ512206 (B. vietnamensis), AJ512207 (B. caryophylli), AJ505317 (B. caribensis), AJ505319 (B. phymatum), and AJ512205 (M. nodulans). nifH sequences from B. fungorum, R. palustris, and R. leguminosarum were from partially completed genome Web sites.

	DISCUSSION

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The widespread character of nodulation by ß-proteobacteria is also attested to by the phylogenetic diversity of the ß-rhizobia identified so far, including one Ralstonia species (1) andthree Burkholderia species (B. caribensis, B. tuberum, and B. phymatum) (24), as well as the fact that they have been isolated from Asia, Africa, and South America. Since many legumes and environments remain to be explored, it is highly likely that further characterization of rhizobia will reveal an even greater diversity. For many decades, standard isolation procedures have been used for rhizobia, and identification as legume symbionts through nodulation tests has required the availability of host plant seeds. These traditional approaches, coupled with the difficulty of obtaining seeds for many tropical legumes, have probably contributed to masking of the natural diversity of rhizobia.

Nitrogen fixation, which is widespread in eubacteria and archaea, is thought to be an ancestral function now lost by many bacteria (3). Conversely, nodulation is thought to have appeared recently in evolution, at the same time as the appearance of legumes on Earth, about 70 to 130 millions years ago. At that period of history, the - and ß-proteobacteria and the different rhizobial lineages already had diverged (22). The genes required for legume nodulation are thought to have been acquired subsequently by lateral transfer from undefined sources, thus converting soil saprophytes into symbionts (7). This hypothesis has been confirmed by recent data (6, 15). The presence in - and ß-rhizobia of very similar and phylogenetically related nodABC genes strongly supports the hypothesis of a unique origin for the common nod genes. However, it is not clear whether a single transfer event was responsible for the spread of nodulation genes from one subclass to the other or whether recurrent transfers occurred between the two subclasses. Our phylogenetic and NodA length analyses together suggest the occurrence of at least two lateral transfers between these two unrelated subclasses of proteobacteria, although statistical analysis did not allow this hypothesis to be ascertained. Further identification of other ß-rhizobia may be useful for confirming such a hypothesis. Moreover, a comparative analysis of the nodA, nifH, and 16S rDNA trees suggests that ß-rhizobia emerged through the transfer of nod genes to diazotrophic ß-proteobacteria. Since the nod and nif genes are located on the same plasmid in the ß-rhizobia investigated, it is possible that exogenous nod and nif genes were cotransferred prior to the replacement of the exogenous nifH gene by the indigenous gene. This level of complexity is in line with the highly complex evolutionary history of the legume-rhizobium symbiosis.

	ACKNOWLEDGMENTS

 
We thank Y. Prin for help in microscopy studies and M. Dukhan for help with photographs. We also thank D. Barker and J. Batut for comments and suggestions.

W.-M. Chen was supported by a grant from the National Science Council, Taipei, Taiwan, Republic of China (NSC 91-2320-B-022-001).

	FOOTNOTES

 
* Corresponding author. Mailing address: Laboratoire des Interactions Plantes-Microorganismes, INRA-CNRS, BP 27, 31 326 Castanet-Tolosan Cedex, France. Phone: (33) 5 61 28 54 49. Fax: (33) 5 61 28 50 61. E-mail: boivin{at}toulouse.inra.fr.

Present address: Department of Biology 3, University of York, P.O. Box 373, York YO10 5YW, United Kingdom.

	REFERENCES

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Chen, W. M., S. Laevens, T. M. Lee, T. Coenye, P. de Vos, M. Mergeay, and P. Vandamme. 2001. Ralstonia taiwanensis sp. nov., isolated from root nodules of Mimosa species and sputum of a cystic fibrosis patient.Int. J. Syst. Evol. Microbiol. 51:1729-1735.[Abstract]
1. W.-M. Chen, E. K. James, A. R. Prescott, M. Kierans, and J. I. Sprent. Nodulation of Mimosa spp. by the ß-proteobacterium Ralstonia taiwanensis. Mol. Plant-Microbe Interact., in press.
2. Deschodt, C. C., and B. W. Strijdom. 1976. Effective nodulation of Aspalathus linearis by rhizobia from other Aspalathus species. Phytophylactica 8:103-104.
3. Fani, R., R. Gallo, and P. Lio. 2000. Molecular evolution of nitrogen fixation: the evolutionary history of the nifD, nifK, nifE, and nifN genes. J. Mol. Evol. 51:1-11.[Medline]
4. Felsenstein, J. 1978. Cases in which parsimony or compatibility methods will be positively misleading. Syst. Zool. 27:401-410.[CrossRef]
5. Felsenstein, J. 1993. PHYLIP (phylogeny inference package), version 3.5c. University of Washington, Seattle.
6. Galibert, F., T. M. Finan, S. R. Long, A. Puhler, P. Abola, F. Ampe, F. Barloy-Hubler, M. J. Barnett, A. Becker, P. Boistard, G. Bothe, M. Boutry, L. Bowser, J. Buhrmester, E. Cadieu, D. Capela, P. Chain, A. Cowie, R. W. Davis, S. Dreano, N. A. Federspiel, R. F. Fisher, S. Gloux, T. Godrie, A. Goffeau, B. Golding, J. Gouzy, M. Gurjal, I. Hernandez-Lucas, A. Hong, L. Huizar, R. W. Hyman, T. Jones, D. Kahn, M. L. Kahn, S. Kalman, D. H. Keating, E. Kiss, C. Komp, V. Lalaure, D. Masuy, C. Palm, M. C. Peck, T. M. Pohl, D. Portetelle, B. Purnelle, U. Ramsperger, R. Surzycki, P. Thebault, M. Vandenbol, F. J. Vorholter, S. Weidner, D. H. Wells, K. Wong, K. C. Yeh, and J. Batut. 2001. The composite genome of the legume symbiont Sinorhizobium meliloti.Science 293:668-672.[Abstract/Free Full Text]
7. Hirsch, A. M., M. R. Lum, and J. A. Downie.2001 . What makes the rhizobia-legume symbiosis so special?Plant Physiol. 127:1484-1492.[Free Full Text]
8. Lortet, G., N. Méar, J. Lorquin, B. Dreyfus, P. de Lajudie, C. Rosenberg, and C. Boivin. 1996. Nod factor thin-layer chromatography profiling as a tool to characterize symbiotic specificity of rhizobial strains: application to Sinorhizobium saheli, S. teranga and Rhizobium sp. strains isolated from Acacia and Sesbania.Mol. Plant-Microbe Interact. 9:736-747.
9. Martinez-Romero, E., and J. Caballero-Mellado. 1996. Rhizobium phylogenies and bacterial genetic diversity. Crit. Rev. Plant Sci. 15:113-140.
9. L. Moulin, G. Béna, C. Boivin-Masson, and T. Stpkowski. Phylogenetic analyses of symbiotic nodulation genes support vertical and lateral gene co-transfer within the Bradyrhizobium genus.Mol. Phylogenet. Evol. , in press.
10. Moulin, L., A. Munive, B. Dreyfus, and C. Boivin-Masson. 2001. Nodulation of legumes by members of the ß-subclass of Proteobacteria.Nature 411:948-950.[CrossRef][Medline]
11. Nicholas, K. B., H. B. Nicholas, Jr., and D. W. Deerfield. 1997. GeneDoc: analysis and visualization of genetic variation. EMBNEW News 4:14.
12. Parker, M. A., and A. Lunk. 2000. Relationships of bradyrhizobia from Platypodium and Machaerium (Papilionoideae: tribe Dalbergieae) on Barro Colorado Island, Panama.Int. J. Syst. Evol. Microbiol. 50:1179-1186.[Abstract]
13. Perret, X., C. Staehelin, and W. J. Broughton. 2000. Molecular basis of symbiotic promiscuity. Microbiol. Mol. Biol. Rev. 64:180-201.[Abstract/Free Full Text]
14. Schultze, M., and A. Kondorosi. 1998. Regulation of symbiotic root nodule development. Annu. Rev. Genet. 32:33-57.[CrossRef][Medline]
15. Sullivan, J. T., and C. W. Ronson. 1998. Evolution of rhizobia by acquisition of a 500-kb symbiosis island that integrates into a phe-tRNA gene. Proc. Natl. Acad. Sci. USA 95:5145-5149.[Abstract/Free Full Text]
16. Suominen, L., C. Roos, G. Lortet, L. Paulin, and K. Lindstrom.2001 . Identification and structure of the Rhizobium galegae common nodulation genes: evidence for horizontal gene transfer. Mol. Biol. Evol. 18:907-916.[Abstract/Free Full Text]
17. Swofford, D. 1998. PAUP*: Phylogenetic Analysis Using Parsimony (and other methods), version 4. Sinauer Associates, Sunderland, Mass.
18. Sy, A., E. Giraud, P. Jourand, N. Garcia, A. Willems, P. de Lajudie, Y. Prin, M. Neyra, M. Gillis, C. Boivin-Masson, and B. Dreyfus.2001 . Methylotrophic Methylobacterium bacteria nodulate and fix nitrogen in symbiosis with legumes. J. Bacteriol. 183:214-220.[Abstract/Free Full Text]
19. Thompson, J. D., T. J. Gibson, F. Plewniak, F. Jeanmougin, and D. G. Higgins. 1997. The CLUSTAL X windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools. Nucleic Acids Res. 25:4876-4882.[Abstract/Free Full Text]
20. Tripathi, A. K. 2002. Rhizobia of the ß-subclass of Proteobacteria: a tale of losing the race.Curr. Sci. 82:8-9.
21. Truchet, G., S. Camut, F. de Billy, R. Odorico, and J. Vasse.1989 . The Rhizobium-legume symbiosis.Protoplasma 149:82-88.[CrossRef]
22. Turner, S. L., and J. P. W. Young.2000 . The glutamine synthetases of rhizobia: phylogenetics and evolutionary implications. Mol. Biol. Evol. 17:309-319.[Abstract/Free Full Text]
23. van Berkum, P., and B. D. Eardly. 1998. Molecular evolutionary systematics of the Rhizobiaceae, p.1 -24. In H. P. Spaink, A. Kondorosi, and P. J. J. Hooykaas (ed.), The Rhizobiaceae. Molecular biology of plant-associated bacteria. Kluwer Academic Publishers, Dordrecht, The Netherlands.
24. Vandamme, P., J. Goris, W. M. Chen, P. de Vos, and A. Willems.2002 . Burkholderia tuberum sp. nov. and Burkholderia phymatum sp. nov., nodulate the roots of tropical legumes. Syst. Appl. Microbiol. 25:507-512.[CrossRef][Medline]
25. Zhang, X. X., S. L. Turner, X. W. Guo, H. J. Yang, F. Debellé, G. P. Yang, J. Dénarié, J. P. W. Young, and F. D. Li. 2000. The common nodulation genes of Astragalus sinicus rhizobia are conserved despite chromosomal diversity. Appl. Environ. Microbiol. 66:2988-2995.[Abstract/Free Full Text]

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