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1.
Ilmara Varotto Roma Neto Renan Augusto Ribeiro Mariangela Hungria 《World journal of microbiology & biotechnology》2010,26(7):1291-1302
Biodiversity of diazotrophic symbiotic bacteria in the tropics is a valuable but still poorly studied resource. The objective
of this study was to determine if a second housekeeping gene, glnII, in addition to the 16S rRNA, can be employed to improve the knowledge about taxonomy and phylogeny of rhizobia. Twenty-three
elite rhizobial strains, very effective in fixing nitrogen with twenty-one herbal and woody legumes (including species from
fourteen tribes in the three subfamilies of the family Leguminosae) were selected for this study; all strains are used as commercial inoculants in Brazil. Complete sequences of the 16S rRNA
and partial sequences (480 bp) of the glnII gene were obtained. The same primers and amplification conditions were successful for sequencing the glnII genes of bacteria belonging to five different rhizobial genera—Bradyrhizobium, Mesorhizobium, Methylobacterium, Rhizobium, Sinorhizobium)—positioned in distantly related branches. The analysis of the concatenated genes (16S rRNA + glnII) considerably improved information about phylogeny and taxonomy of rhizobia in comparison to the single analysis of the 16S
rRNA. Nine strains might belong to new species. The complementary analysis of the glnII gene was successful with all strains and improved the phylogenetic clustering and clarified the taxonomic position of several
strains. The strategy of including the analysis of glnII, in addition to the 16S rRNA, is cost- and time- effective for the characterization of large rhizobial culture collections
or in surveys of many isolates. 相似文献
2.
Li Li Han En Tao Wang Yang Li Lu Yong Fa Zhang Xin Hua Sui Wen Feng Chen Wen Xin Chen 《Journal of microbiology (Seoul, Korea)》2009,47(3):287-296
Adzuki bean (Vigna angularis) is an important legume crop native to China, but its rhizobia have not been well characterized. In the present study, a
total of 60 rhizobial strains isolated from eight provinces of China were analyzed with amplified 16S rRNA gene RFLP, IGS-RFLP,
and sequencing analyses of 16S rRNA, atpD, recA, and nodC genes. These strains were identified as genomic species within Rhizobium, Sinorhizobium, Mesorhizobium, Bradyrhizobium, and Ochrobactrum. The most abundant groups were Bradyrhizobium species and Sinorhizobium fredii. Diverse nodC genes were found in these strains, which were mainly co-evolved with the housekeeping genes, but a possible lateral transfer
of nodC from Sinorhizobium to Rhizobium was found. Analyses of the genomic and symbiotic gene backgrounds showed that adzuki bean shared the same rhizobial gene
pool with soybean (legume native to China) and the exotic Vigna species. All of these data demonstrated that nodule formation is the interaction of rhizobia, host plants, and environment
characters.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
3.
Li QQ Wang ET Zhang YZ Zhang YM Tian CF Sui XH Chen WF Chen WX 《Microbial ecology》2011,61(4):917-931
A total of 215 rhizobial strains were isolated and analyzed with 16S rRNA gene, 16S–23S intergenic spacer, housekeeping genes
atpD, recA, and glnII, and symbiotic genes nifH and nodC to understand the genetic diversity of soybean rhizobia in Hebei province, China. All the strains except one were symbiotic
bacteria classified into nine genospecies in the genera of Bradyrhizobium and Sinorhizobium. Surveys on the distribution of these rhizobia in different regions showed that Bradyrhizobium japonicum and Bradyrhizobium elkanii strains were found only in neutral to slightly alkaline soils whereas Bradyrhizobium yuanmingense, Bradyrhizobium liaoningense-related strains and strains of five Sinorhizobium genospecies were found in alkaline–saline soils. Correspondence and canonical correspondence analyses on the relationship
of rhizobial distribution and their soil characteristics reveal that high soil pH, electrical conductivity, and potassium
content favor distribution of the B. yuanmingense and the five Sinorhizobium species but inhibit B. japonicum and B. elkanii. High contents of available phosphorus and organic matters benefit Sinorhizobium fredii and B. liaoningense-related strains and inhibit the others groups mentioned above. The symbiotic gene (nifH and nodC) lineages among B. elkanii, B. japonicum, B. yuanmingense, and Sinorhizobium spp. were observed in the strains, signifying that vertical gene transfer was the main mechanism to maintain these genes
in the soybean rhizobia. However, lateral transfer of symbiotic genes commonly in Sinorhizobium spp. and rarely in Bradyrhizobium spp. was also detected. These results showed the genetic diversity, the biogeography, and the soil determinant factors of
soybean rhizobia in Hebei province of China. 相似文献
4.
Symbiotic effectiveness of 19 indigenous and two exotic (USDA 2426 and USDA 2431) strains of lentil Rhizobium belonging to different phage-sensitive and phage-resistant groups was compared under axenic condition. Four strains (USDA
2431, BHULR 104, BHULR 113, and BHULR 115) sensitive to different phages were found significantly superior over others in
terms of nodule number, acetylene reduction activity, and total dry weight per plant. Inoculation response of these strains
was then evaluated on six lentil cultivars under field condition. A significant symbiotic interaction between rhizobial strains
and lentil cultivars was observed. Grain yield enhancement was noticed by the compatible interaction of lentil cultivars HUL-57,
L-4147, K-75, and PL-4/DPL-15/DPL-62 with rhizobial strains USDA 2431, BHULR 104, BHULR 113, and BHULR 115, respectively.
The authentication of rhizobial strains was accomplished through 16S rDNA sequence analysis. All rhizobial strains had close
matching with R. leguminosarum bv. viciae strains. The results have shown that phages can trustfully help selecting out the symbiotically efficient most rhizobial
strains for advantageous use with lentil cultivars, in order to strengthen the BNF-based future lentil breeding programs. 相似文献
5.
AR Torres G Kaschuk GP Saridakis M Hungria 《World journal of microbiology & biotechnology》2012,28(4):1831-1835
Brazil has succeeded in sustaining production of soybean [Glycine max (L.) Merrill] by relying mainly on symbiotic N2 fixation, thanks to the selection and use in inoculants of very effective strains of Bradyrhizobium japonicum and Bradyrhizobium elkanii. It is desirable that rhizobial strains used in inoculants have stable genetic and physiological traits, but experience confirms
that rhizobial strains nodulating soybean often lose competitiveness in the field. In this study, soybean cultivar BR 16 was
single-inoculated with four B. japonicum strains (CIAT 88, CIAT 89, CIAT 104 and CIAT 105) under aseptic conditions. Forty colonies were isolated from nodules produced
by each strain. The progenitor strains, the isolates and four other commercially recommended strains were applied separately
to the same cultivar under controlled greenhouse conditions. We observed significant variability in nodulation, shoot dry
weight, shoot total N, nodule efficiency (total N mass over nodule mass) and BOX-PCR fingerprinting profiles between variant
and progenitor strains. Some variant strains resulted in significantly larger responses in terms of shoot total N, dry weight
and nodule efficiency, when compared to their progenitor strain. These results highlight the need for intermittent evaluation
of stock bacterial cultures to guarantee effective symbiosis after inoculation. Most importantly, it indicates that it is
possible to improve symbiotic effectiveness by screening rhizobial strains for higher N2 fixation capacity within the natural variability that can be found within each progenitor strain. 相似文献
6.
Diouf D Samba-Mbaye R Lesueur D Ba AT Dreyfus B de Lajudie P Neyra M 《Microbial ecology》2007,54(3):553-566
The occurrence and the distribution of rhizobial populations naturally associated to Acacia seyal Del. were characterized in 42 soils from Senegal. The diversity of rhizobial genotypes, as characterized by polymerase chain
reaction restriction fragment length polymorphism (RFLP) analysis of 16S–23S rDNA, performed on DNA extracted from 138 nodules
resulted in 15 clusters. Results indicated the widespread occurrence of compatible rhizobia associated to A. seyal in various ecogeographic areas. However, the clustering of rhizobial populations based on intergenic spacer (IGS) RFLP profiles
did not reflect their geographic origin. Four genera were discriminated on the basis of 16S rRNA gene sequences of the strains
representative for the IGS-RFLP profiles. The majority of rhizobia associated to A. seyal were affiliated to Mesorhizobium and Sinorhizobium 64 and 29%, respectively, of the different IGS-RFLP profiles. Our results demonstrate the coexistence inside the nodule of
plant-pathogenic non-N2-fixing Agrobacterium and Burkholderia strains, which induced the formation of ineffective nodules, with symbiotic rhizobia. Nodulation was recorded in saline soils
and/or at low pH values or in alkaline soils, suggesting adaptability of natural rhizobial populations to major ecological
environmental stress and their ability to establish symbiotic associations within these soil environments. These results contribute
to the progressing research efforts to uncover the biodiversity of rhizobia and to improve nitrogen fixation in agroforestry
systems in sub-Saharan Africa. 相似文献
7.
Gene Sequence Phylogenies of the Family <Emphasis Type="Italic">Microbacteriaceae</Emphasis> 总被引:1,自引:0,他引:1
The type strains of 32 species of 13 genera of the family Microbacteriaceae were analysed with respect to gene-coding phylogeny for DNA gyrase subunit B (gyrB), RNA-polymerase subunit B (rpoB), recombinase A (recA), and polyphosphate kinase (ppk). The resulting gene trees were compared with the 16S rRNA gene phylogeny of the same strains. The topology of neighbour-joining
and maximum parsimony phylogenetic trees, based on nucleic-acid sequences and protein sequences of housekeeping genes, differed
from one another, and no gene tree was identical to that of the 16S rRNA gene tree. Most genera analysed containing >1 strain
formed phylogenetically coherent taxa. The three pathovars of Curtobacterium flaccumfaciens clustered together to the exclusion of the type strains of other Curtobacterium species in all DNA - and protein-based analyses. In no tree did the distribution of a major taxonomic marker, i.e., diaminobutyric acid versus lysine and/or ornithine in the peptidoglycan, or acyl type of peptidoglycan, correlate with the
phylogenetic position of the organisms. The changing phylogenetic position of Agrococcus jenensis was unexpected: This strain defined individual lineages in the trees based on 16S rRNA and gyrB and showed identity with Microbacterium saperdae in the other three gene trees. 相似文献
8.
Knowledge of rhizobium diversity is helping to enable the utilization of rhizobial resources. To analyze the phenotypic and genetic diversity and the symbiotic divergence of rhizobia of Medicago sativa, 30 endophytic and non-endophytic isolates were collected from different parts of five alfalfa varieties in three geographic locations in Gansu, China. Numerical analyses based on 72 phenotypic properties and restriction fragment length polymorphism (RFLP) fingerprinting indicated the abundant phenotypic and genetic diversity of the tested strains. According to the phylogenetic analysis of 16S RNA, atpD, glnII, and recA gene sequences, Rhizobium and Ensifer were further classified into four different genotypes: Rhizobium radiobacter, Rhizobium sp., Rhizobium rosettiformans, and Ensifer meliloti. The differences in architecture and functioning of the rhizobial genomes and, to a lesser extent, environment diversification helped explain the diversity of tested strains. The tested strains exhibited similar symbiotic feature when inoculated onto M. sativa cvs. Gannong Nos. 3 and 9 and Qingshui plants for the clustering feature of their parameter values. An obvious symbiotic divergence of rhizobial strains was observed in M. sativa cvs. Longzhong and WL168HQ plants because of the scattered parameter values. Their symbiotic divergence differed according to alfalfa varieties, which indicated that the sensitivity of different alfalfa varieties to rhizobial strains may differ. Most of the tested strains exhibited plant growth-promoting traits including phosphate solubilization and production of indole-3-acetic acid (IAA) when colonizing plant tissues and soil. 相似文献
9.
Howard Langer Kemanthi G. Nandasena John G. Howieson Milko Jorquera Fernando Borie 《World journal of microbiology & biotechnology》2008,24(3):301-308
A study was conducted with the aim of evaluating the genetic diversity of alfalfa rhizobia isolated from volcanic soils in
southern Chile and their ability to establish an effective symbiosis with alfalfa. Rhizobial strains isolated from nodules
were identified and selected based on PCR analyses and acid tolerance. Symbiotic effectiveness (nodulation and shoot dry weight)
of acid-tolerant rhizobia was evaluated in glasshouse experiments under acidic conditions. The results revealed that Sinorhizobium meliloti is the dominant species in alfalfa nodules with a high genetic diversity at strain level grouped in three major clusters.
There was a close relationship (r
2 = 0.895, P ≤ 0.001, n = 40) between soil pH and the size of rhizobial populations. Representative isolates from major cluster groups showed wide
variation in acid tolerance expressed on buffered agar plates (pH 4.5–7.0) and symbiotic effectiveness with alfalfa. One isolate
(NS11) appears to be suitable as an inoculant for alfalfa according to its acid tolerance and symbiotic effectiveness at low
pH (5.5). The isolation and selection of naturalized S. meliloti strains with high symbiotic effectiveness under acidic conditions is an alternative approach to improving the productivity
of alfalfa and for reducing the application of synthetic fertilizers in Chile. 相似文献
10.
Rodica C. Efrose Craita M. Rosu Catalina Stedel Andrei Stefan Culita Sirbu Lucian D. Gorgan Nikolaos E. Labrou Emmanouil Flemetakis 《Antonie van Leeuwenhoek》2018,111(1):135-153
The symbiotic nitrogen fixing legumes play an essential role in sustainable agriculture. White clover (Trifolium repens L.) is one of the most valuable perennial legumes in pastures and meadows of temperate regions. Despite its great agriculture and economic importance, there is no detailed available information on phylogenetic assignation and characterization of rhizobia associated with native white clover plants in South-Eastern Europe. In the present work, the diversity of indigenous white clover rhizobia originating in 11 different natural ecosystems in North-Eastern Romania were assessed by a polyphasic approach. Initial grouping showed that, 73 rhizobial isolates, representing seven distinct phenons were distributed into 12 genotypes, indicating a wide phenotypic and genotypic diversity among the isolates. To clarify their phylogeny, 44 representative strains were used in sequence analysis of 16S rRNA gene and IGS fragments, three housekeeping genes (atpD, glnII and recA) and two symbiosis-related genes (nodA and nifH). Multilocus sequence analysis (MLSA) phylogeny based on concatenated housekeeping genes delineated the clover isolates into five putative genospecies. Despite their diverse chromosomal backgrounds, test strains shared highly similar symbiotic genes closely related to Rhizobium leguminosarum biovar trifolii. Phylogenies inferred from housekeeping genes were incongruent with those of symbiotic genes, probably due to occurrence of lateral transfer events among native strains. This is the first polyphasic taxonomic study to report on the MLSA-based phylogenetic diversity of indigenous rhizobia nodulating white clover plants grown in various soil types in South-Eastern Europe. Our results provide valuable taxonomic data on native clover rhizobia and may increase the pool of genetic material to be used as biofertilizers. 相似文献
11.
Hadjira Ahnia Farida Boulila Abdelghani Boulila Karima Boucheffa David Durán Yasmina Bourebaba Adouda Salmi Juan Imperial Tomás Ruiz-Argüeso Luis Rey 《Antonie van Leeuwenhoek》2014,105(6):1121-1129
Fifty-one rhizobial strains isolated from root nodules of Cytisus villosus growing in Northeastern Algeria were characterized by genomic and phenotypic analyses. Isolates were grouped into sixteen different patterns by PCR-RAPD. The phylogenetic status of one representative isolate from each pattern was examined by multilocus sequence analyses of four housekeeping genes (16S rRNA, glnII, recA, and atpD) and one symbiotic gene (nodC). Analysis of 16S rRNA gene sequences showed that all the isolates belonged to the genus Bradyrhizobium. Phylogenetic analyses based on individual or concatenated genes glnII, recA, and atpD indicated that strains cluster in three distinct groups. Ten out of the sixteen strains grouped together with Bradyrhizobium japonicum, while a second group of four clustered with Bradyrhizobium canariense. The third group, represented by isolates CTS8 and CTS57, differed significantly from all other bradyrhizobia known to nodulate members of the Genisteae tribe. In contrast with core genes, sequences of the nodC symbiotic gene from all the examined strains form a homogeneous group within the genistearum symbiovar of Bradyrhizobium. All strains tested nodulated Lupinus angustifolius, Lupinus luteus, and Spartium junceum but not Glycine max. From these results, it is concluded that C. villosus CTS8 and CTS57 strains represent a new lineage within the Bradyrhizobium genus. 相似文献
12.
Analysis of genetic diversity among indigenous rhizobia and its symbiotic effectiveness with soybean cultivar is important
for development of knowledge about rhizobial ecology. In India, little is known about the genetic resources and diversity
of rhizobia nodulating soybean. Indigenous bradyrhizobia isolated from root nodules of soybean plants, collected from traditional
cultivating regions of two states (Madhya Pradesh and Uttar Pradesh) of India, were screened for bacteriophage sensitivity
to identify successful broad host range symbiotic effectivity. Of 172 rhizobial isolates, 91 showed sensitivities to eight
lytic phages and form ten groups on the basis of sensitivity patterns. The genetic diversity of 23 isolates belonging to different
phage groups was assessed along with that of strains USDA123 and USDA94 by the restriction fragment length polymorphism (RFLP)
analysis of 16S rDNA, intergenic spacer (IGS) (16S–23S rDNA), and DnaK regions. RFLP analysis of 16S rDNA formed 5 groups, whereas 19 and 9 groups were revealed by IGS and the DnaK genes, respectively. The IGS regions showed many amplified polymorphic bands. Nine isolates which revealed high RFLP polymorphism
in the abovementioned regions (16S rRNA, IGS, DnaK) were used for 16S rRNA sequence analyses. The results indicate that taxonomically, all isolates were related to Rhizobium etli, Bradyrhizobium spp., and Bradyrhizobium yuanmingense. The doubling time of isolates varied from 9 h (MPSR155) to 16.2 h (MPSR068) in YM broth. Five isolates which did not show
cross infectivity with isolated phage strains were studied for symbiotic efficiency. All isolates showed broad host range
symbiotic effectiveness forming effective nodules on Vigna mungo, Vigna radiata, Vigna unguiculata, and Cajanus cajan. The present study provides information on genetic diversity and host range symbiosis of indigenous soybean rhizobia typed
by different phages. 相似文献
13.
Jerzy Wielbo Dominika Kidaj Piotr Koper Agnieszka Kubik-Komar Anna Skorupska 《Central European Journal of Biology》2012,7(1):13-24
Background
Rhizobium leguminosarum bv. viciae (Rlv) is a soil bacterium which can form nitrogen-fixing symbiotic relationships with leguminous plants. Numerous rhizobial strains found in soils compete with each other. Competition can occur both during the saprophytic growth phase in the rhizosphere and inside plant tissues, during the symbiotic phase. Competition is important as it may affect the composition of rhizobial populations present in the soil and in the root nodules of plants. 相似文献14.
Pâmela Menna Alan Alves Pereira Eliane Villamil Bangel Mariangela Hungria 《Symbiosis (Philadelphia, Pa.)》2009,48(1-3):120-130
With more than 30 million doses of rhizobial inoculants marketed per year, it is probable that Brazilian agriculture benefits more than any other country from symbiotic N2 fixation. As a result of strain-selection programs, 142 strains of rhizobia are officially recommended for use in commercial inoculants for ninety-six leguminous crops. In this study, sixty-eight of these elite strains were characterized by rep-PCR with the BOX-primer. Reproducibility of the DNA profiles was confirmed, suggesting efficacy of BOX-PCR both for control of quality of inoculants and for preliminary characterization of rhizobial culture collections. Strains of different species never showed similarity higher than 70% in the BOX-PCR analysis, however, some strains of the same species fit into more than one cluster, and correlation between BOX-PCR products and l6S rRNA sequences was low (7.6%). On the other hand, a polyphasic approach — 20%∶80% of BOX-PCR:16S rRNA which correlated well with the l6S rRNA analysis (95%), and provided higher definition of the genotypes, resulting in clearer indications of the taxonomic groups — might expedite rhizobial diversity studies. 相似文献
15.
Within the framework of our study, we assessed the nodule occupancy of a mixture of various strains of rhizobia to inoculate
several provenances of Acacia senegal and Acacia nilotica. The first part of the experiment was carried out under greenhouse conditions where the plants were cultivated in polyvinyl
chloride tubes containing an unsterilized Sangalkam soil low in organic matter and nitrogen. The results showed that 4 and
8 months after sowing, rhizobial strains CIRADF 306 and CIRADF 300 were mainly present in nodules of A. nilotica and A. senegal, respectively. After transferring the seedlings to the more fertile soil in Bel Air field station, the molecular analysis
of the nodules showed that strain CIRADF 306 was absent from the nodules of A.
nilotica, whereas strain CIRADF 305 which occurred only at low nodule occupancy in the nursery, predominated in the field conditions.
On the other hand, strain CIRADF 300 occurred in the majority of the nodules from the various provenances of A. senegal. These results demonstrated actual interaction between inoculated rhizobial strains, soil type and host plant genotype in
terms of competitiveness, nodulation and symbiotic nitrogen fixation. 相似文献
16.
A phylogenetic analysis of selected symbiotic Nostoc strain sequences and available database 16S rDNA sequences of both symbiotic and free-living cyanobacteria was carried out using maximum likelihood and Bayesian inference techniques. Most of the symbiotic strains fell into well separated clades. One clade consisted of a mixture of symbiotic and free-living isolates. This clade includes Nostoc sp. strain PCC 73102, the reference strain proposed for Nostoc punctiforme. A separate symbiotic clade with isolates exclusively from Gunnera species was also obtained, suggesting that not all symbiotic Nostoc species can be assigned to N. punctiforme. Moreover, isolates from Azolla filiculoides and one from Gunnera dentata were well nested within a clade comprising most of the Anabaena sequences. This result supports the affiliation of the Azolla isolates with the genus Anabaena and shows that strains within this genus can form symbioses with additional hosts. Furthermore, these symbiotic strains produced hormogonia, thereby verifying that hormogonia formation is not absent in Anabaena and cannot be used as a criterion to distinguish it from Nostoc.The GenBank accession numbers for the cyanobacterial 16S rRNA gene sequences determined in this study are AY742447-AY742454. 相似文献
17.
The plasticity of rhizobial genomes is far greater than previously thought, with complex genomic recombination events that
may be accelerated by the often stressful environmental conditions of the tropics. This study aimed at evaluating changes
in soybean rhizobia due to adaptation to inhospitable environmental conditions (high temperatures, drought, and acid soils)
in the Brazilian Cerrados. Both the host plant and combinations of four strains of soybean Bradyrhizobium were introduced in an uncropped soil devoid of rhizobia capable of nodulating soybean. After the third year, seeds were not
reinoculated. Two hundred and sixty-three isolates were obtained from nodules of field-grown soybean after the seventh year,
and their morphological, physiological, serological, and symbiotic properties determined, followed by genetic analysis of
conserved and symbiotic genes. B. japonicum strain CPAC 15 (same serogroup as USDA 123) was characterized as having high saprophytic capacity and competitiveness and
by the seventh year represented up to 70% of the cultivable population, in contrast to the poor survival and competitiveness
of B. japonicum strain CPAC 7 (same serogroup as CB 1809). In general, adapted strains had increased mucoidy, and up to 43% of the isolates
showed no serological reaction. High variability, presumably resulting from the adaptation to the harsh environmental conditions,
was verified in rep-PCR (polymerase chain reaction) profiles, being lower in strain CPAC 15, intermediate in B. elkanii, and higher in CPAC 7. Restriction fragment length polymorphism (RFLP)-PCR types of the 16S rDNA corresponded to the following:
one type for B. elkanii species, two for B. japonicum, associated to CPAC 15 and CPAC 7, and unknown combinations of profiles. However, when nodC sequences and RFLP-PCR of the nifH region data were considered, only two clusters were observed having full congruence with B. japonicum and B. elkanii species. Combining the results, variability was such that even within a genetically more stable group (such as that of CPAC
15), only 6.4% of the isolates showed high similarity to the inoculant strain, whereas none was similar to CPAC 7. The genetic
variability in our study seems to result from a variety and combination of events including strain dispersion, genomic recombination,
and horizontal gene transfer. Furthermore, the genetic variability appears to be mainly associated with adaptation, saprophytic
capacity, and competitiveness, and not with symbiotic effectiveness, as the similarity of symbiotic genes was higher than
that of conserved regions of the DNA. 相似文献
18.
A multilocus phylogenetic approach was applied to elucidate the phylogeny of Astragalus cicer rhizobia derived from Poland, Ukraine, and Canada. The strains selected for the studies represented three main geographically
different phenons of these bacteria. Phylogenetic analyses were performed with three chromosomal housekeeping loci (16S rRNA,
atpD, glnII) and three symbiotic genes located on a plasmid (nodA, nodC, nifH). The “core” and “auxiliary” gene trees revealed that A. cicer nodule isolates were intermingled with the strains of Mesorhizobium species, which implies that they are descendents of the same ancestor as mesorhizobia and fall into the Mesorhizobium genus. The noted congruence of the housekeeping and symbiotic gene phylogenies of A. cicer microsymbionts indicates that sym loci are transferred to these bacteria through vertical transmission without a significant participation of intergeneric
horizontal gene spread. All the three sym gene sequences of the Polish and Ukrainian A. cicer nodule isolates were more closely related to one another than to the corresponding sequences of the Canadian isolates. The
phylogeographic patterns of the sym genes of intercontinental strains point to their relatively long, separate, evolutionary history. 相似文献
19.
Kai Wei Xu Petri Penttinen Yuan Xue Chen Qiang Chen Xiaoping Zhang 《Applied microbiology and biotechnology》2013,97(2):783-793
In search of effective nitrogen-fixing strains for inoculating Leucaena leucocephala, we assessed the symbiotic efficiency of 41 rhizobial isolates from root nodules of L. leucocephala growing in the arid–hot river valley area in Panxi, China. The genetic diversity of the isolates was studied by analyzing the housekeeping genes 16S rRNA and recA, and the symbiotic genes nifH and nodC. In the nodulation and symbiotic efficiency assay, only 11 of the 41 isolates promoted the growth of L. leucocephala while the majority of the isolates were ineffective in symbiotic nitrogen fixation. Furthermore, one fourth of the isolates had a growth slowing effect on the host. According to the 16S rRNA and recA gene analyses, most of the isolates were Ensifer spp. The remaining isolates were assigned to Rhizobium, Mesorhizobium and Bradyrhizobium. The sequence analyses indicated that the L. leucocephala rhizobia had undergone gene recombination. In contrast to the promiscuity observed as a wide species distribution of the isolates, the results implied that L. leucocephala is preferentially nodulated by strains that share common symbiosis genes. The symbiotic efficiency was not connected to chromosomal background of the symbionts and isolates carrying a similar nifH or nodC showed totally different nitrogen fixation efficiency. 相似文献
20.
Mariangela Hungria Lígia Maria O. Chueire Manuel Megías Youssef Lamrabet Agustin Probanza Francisco J. Guttierrez-Mañero Rubens J. Campo 《Plant and Soil》2006,288(1-2):343-356
This study characterized genetically 30 fast-growing rhizobial strains isolated from nodules of Asian and modern soybean genotypes that had been inoculated with soils from disparate regions of Brazil. Analyses by rep-PCR (ERIC and REP) and RAPD indicated a high level of genetic diversity among the strains. The RFLP-PCR and sequencing analysis of the 16S rRNA genes indicated that none of the strains was related to Sinorhizobium (Ensifer) fredii, whereas most were related to Rhizobium tropici (although they were unable to nodulate Phaseolus vulgaris) and to Rhizobium genomic species Q. One strain was related to Rhizobium sp. OR 191, while two others were closely related to Agrobacterium (Rhizobium) spp.; furthermore, symbiotic effectiveness with soybean was maintained in those strains. Five strains were related to Bradyrhizobium japonicum and B. elkanii, with four of them being similar to strains carried in Brazilian inoculants, therefore modifications in physiological properties, as a shorter doubling time might have resulted from adaptation to local conditions. Phospholipid fatty acid analysis (PFLA) was less precise in delineating taxonomic relationships. The strains fit into eight Nod-factor profiles that were related to rhizobial species, but not to N2-fixation capacity or competitiveness. The data obtained highlight the diversity and promiscuity of rhizobia in the tropics, being capable of nodulating exotic legumes and might reflect ecological strategies to survive in N-poor soils; in addition, the diversity could also represent an important source of efficient and competitive rhizobial strains for the tropics. Putative new rhizobial species were detected only in undisturbed soils. Three species (R. tropici, B. japonicum and B. elkanii) were found under the more sustainable management system known as no-till, while the only species isolated from soils under conventional till was R. tropici. Those results emphasize that from the moment that agriculture was introduced into undisturbed soils rhizobial diversity has changed, being drastically reduced when a less sustainable soil management system was adopted. 相似文献