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PubMed2026

Mesorhizobium bavaricum sp. nov. and Mesorhizobium monacense sp. nov., two novel Lotus-associated species harbouring symbiotic plasmids.

Legumes establish a mutualistic interaction with nitrogen-fixing rhizobia. Lotus japonicus is a model for studying this symbiosis; however, only a limited number of rhizobial species nodulating this host have been taxonomically described. Here, we characterise four Mesorhizobium strains (DC-1.1T, Qj1B1, DC-1.5T, and Qj2B2) isolated from root nodules of Lotus japonicus and Lotus burttii. Multi-locus phylogeny and phylogenomic analyses resolved these isolates into two well-supported monophyletic clades. Genome-based comparisons supported their classification as distinct taxa, with strains DC-1.1T and Qj1B1 showing 95.2% average nucleotide identity (ANI) and 62.9-63.5% digital DNA-DNA hybridisation (dDDH) values relative to Mesorhizobium newzealandense ICMP 19545T, whereas DC-1.5T and Qj2B2 exhibited 92.5-92.8% ANI and 49.9-50.5% dDDH compared with Mesorhizobium waimense ICMP 19557T. Together with chemotaxonomic and physiological traits, these data support the proposal of two novel species, Mesorhizobium bavaricum sp. nov. (DC-1.1T and Qj1B1) and Mesorhizobium monacense sp. nov. (DC-1.5T and Qj2B2). Metagenomic analyses predicted high environmental prevalence for these novel taxa, particularly within soil habitats. Isolates DC-1.1T, Qj1B1, and DC-1.5T effectively nodulated Lotus burttii and significantly promoted plant growth, whereas Qj2B2 neither nodulated nor enhanced growth. Comparative genomic analysis revealed that the nodulating isolates harbour symbiotic genes (nod, fix, and nif) on symbiotic plasmids, a rare feature in Mesorhizobium strains, whereas Qj2B2 lacks essential nod and nif genes. Consistent with these genomic features, symbiotaxonomic analysis assigned the nodulating isolates to symbiovar loti. These results highlight the potential of these isolates as models for comparative analyses of symbiotic plasmid evolution and horizontal gene transfer.

Mesorhizobium↗
PubMed2004

Mesorhizobium septentrionale sp. nov. and Mesorhizobium temperatum sp. nov., isolated from Astragalus adsurgens growing in the northern regions of China.

Ninety-five rhizobial strains isolated from Astragalus adsurgens growing in the northern regions of China were classified into three main groups, candidate species I, II and III, based on a polyphasic approach. Comparative analysis of full-length 16S rRNA gene sequences of representative strains showed that candidate species I and II were Mesorhizobium, while candidate species III, which consisted of non-nodulating strains, was closely related to Agrobacterium tumefaciens. The phylogenetic relationships of the three candidate species and some related strains were also confirmed by the sequencing of glnA genes, which were used as an alternative chromosomal marker. The DNA-DNA relatedness was between 11.3 and 47.1 % among representative strains of candidate species I and II and the type strains of defined Mesorhizobium species. Candidate III had DNA relatedness of between 4.3 and 25.2 % with type strains of Agrobacterium tumefaciens and Agrobacterium rubi. Two novel species are proposed to accommodate candidate species I and II, Mesorhizobium septentrionale sp. nov. (type strain, SDW014(T)=CCBAU 11014(T)=HAMBI 2582(T)) and Mesorhizobium temperatum sp. nov. (type strain, SDW018(T)=CCBAU 11018(T)=HAMBI 2583(T)), respectively. At least two distinct nodA sequences were identified among the strains. The numerically dominant nodA sequence type was most similar to that from the Mesorhizobium tianshanense type strain and was identified in strains belonging to the two novel species as well as other, as yet, undefined genome types. Host range studies indicate that the different nodA sequences correlate with different host ranges. Further comparative studies with the defined Agrobacterium species are needed to clarify the taxonomic identity of candidate species III.

Acyltransferases↗
PubMed2002

Lipopolysaccharides from Mesorhizobium huakuii and Mesorhizobium ciceri: chemical and immunological comparative data.

Lipopolysaccharides of two Mesorhizobium species of different host specificity were compared: M. huakuii and M. ciceri. M. huakuii sp. was represented by five strains with special consideration of M. huakuii IFO 15243(T). SDS/PAGE profiles revealed that all M. huakuii LPS preparations contained low molecular mass fractions (LPS-II) of the same molecular size. All of lipopolysaccharides contained high molecular mass fractions (LPS-I). However, the high molecular mass fraction from each strain possessed an individual molecular size distribution pattern. The crossreactivity of blotted lipopolysaccharides with rabbit polyclonal antibodies against Mesorhizobium huakuii IFO 15243(T) whole bacteria indicated the presence of common epitope(s) within the investigated Mesorhizobium huakuii strains. Moreover, LPS from M. huakuii S52 also reacted with anti M. ciceri HAMBI 1750 serum showing that there are epitopes common for different mesorhizobial species. LPS isolated from Mesorhizobium huakuii strain IFO 15243(T) contained neutral sugars: L-6-deoxytalose, L-rhamnose, D-galactose and D-glucose, aminosugars:D-quinovosamine, D-glucosamine, D-2,3-diamino-2,3-dideoxyglucose and D-galacturonic and D-glucuronic acids. In the LPS preparation, fatty acids typical for Mesorhizobium strains were detected. 3-Hydroxydodecanoic, 3-hydroxy-iso-tridecanoic, 3-hydroxyeicosanoic, 3-hydroxyheneicosanoic and 3-hydroxydocosenoic acids were the major amide linked fatty acids, while iso -heptadecanoic, eicosanoic, docosenoic, as well as 27-hydroxyoctacosanoic and 27-oxooctacosanoic acids were the dominant ester linked fatty residues.

Alphaproteobacteria↗
PubMed2000

Analysis of cellular fatty acids and phenotypic relationships of Agrobacterium, Bradyrhizobium, Mesorhizobium, Rhizobium and Sinorhizobium species using the Sherlock Microbial Identification System.

Previous studies have demonstrated that cellular fatty acid analysis is a useful tool for identifying unknown strains of rhizobia and establishing taxonomic relationships between the species. In this study, the fatty acid profiles of over 600 strains belonging to the genera Agrobacterium, Bradyrhizobium, Mesorhizobium, Rhizobium and Sinorhizobium were evaluated using the gaschromatography-based Sherlock Microbial Identification System (MIS). Data collected with the MIS showed that the three phylogenetically defined biovars of the genus Agrobacterium formed discrete clusters, whilst species belonging to the genus Mesorhizobium formed three subclusters which were easily distinguished. These three subclusters contained Mesorhizobium ciceri and Mesorhizobium mediterraneum, Mesorhizobium tianshanense fatty acid group I and Mesorhizobium plurifarium, and Mesorhizobium huakuii and Mesorhizobium loti. The genus Sinorhizobium was composed of an individual position for Sinorhizobium meliloti and a large cluster comprising Sinorhizobium fredii, Sinorhizobium saheli, Sinorhizobium terangae, Sinorhizobium kostiense and Sinorhizobium arboris. S. meliloti contained significantly higher levels of the fatty acid 19:0 cyclo omega 8 cis and clustered with Rhizobium sp. (Hedysarum coronarium). However, discrimination between the species of genera Sinorhizobium and Rhizobium was a function of the concentration of 16:0 3-OH. The genus Rhizobium contained a single cluster containing Rhizobium sp. (Hedysarum coronarium), Rhizobium gallicum, Rhizobium leguminosarum and Rhizobium etli, along with individual positions for Rhizobium giardinii, Rhizobium tropici, Rhizobium galegae and Rhizobium hainanense. R. tropici and R. hainanense exhibited similarity to Agrobacterium biovar 2, whilst R. galegae was similar to Agrobacterium biovar 1. R. giardinii appeared unique, with comparatively little similarity to the other species. Analysis of the genus Bradyrhizobium revealed large differences from the other genera studied. Two subgroups of Bradyrhizobium elkanii were detected and easily distinguished from Bradyrhizobium japonicum. Bradyrhizobium liaoningense and Bradyrhizobium sp. (Arachis hypogaea), a group isolated from Chinese peanut plants, showed similarities to B. japonicum, whilst a subgroup of M. tianshanense appeared identical to Bradyrhizobium sp. (Arachis hypogaea).

Bacterial Typing Techniques↗
PubMed2006

Mesorhizobium thiogangeticum sp. nov., a novel sulfur-oxidizing chemolithoautotroph from rhizosphere soil of an Indian tropical leguminous plant.

The bacterial strain SJT(T), along with 15 other mesophilic, neutrophilic and facultatively sulfur-oxidizing chemolithotrophic isolates, was isolated by enrichment on reduced sulfur compounds as the sole energy and electron source from soils immediately adjacent to the roots of Clitoria ternatea, a slender leguminous herb of the Lower Gangetic plains of India. Strain SJT(T) was able to oxidize thiosulfate and elemental sulfur for chemolithoautotrophic growth. 16S rRNA and recA gene sequence-based phylogenetic analyses showed that the Gram-negative rod-shaped bacterium belonged to the genus Mesorhizobium and was most closely related to Mesorhizobium loti, Mesorhizobium plurifarium, Mesorhizobium amorphae and Mesorhizobium chacoense. Unequivocally low 16S rRNA (<97 %) and recA (< or =88 %) gene sequence similarities to all existing species of the most closely related genera, a unique fatty acid profile, a distinct G+C content (59.6 mol%) and phenotypic characteristics all suggested that strain SJT(T) represents a novel species. DNA-DNA hybridization and SDS-PAGE analysis of whole-cell proteins also confirmed the taxonomic uniqueness of SJT(T). It is therefore proposed that isolate SJT(T) (= LMG 22697T = MTCC 7001T) be classified as the type strain of a novel species, Mesorhizobium thiogangeticum sp. nov.

Bacterial Proteins↗
PubMed2000

Occurrence and taxonomic significance of oxo-fatty acids in lipopolysaccharides from members of Mesorhizobium.

Lipopolysaccharides (LPSs) isolated from seven strains of Mesorhizobium were studied for the presence of fatty acids with particular attention for 27-oxooctacosanoic acid and 4-oxo fatty acids. The LPSs from all analysed strains contained various amounts of 27-oxo-28:0 and all of them, with the exception of Mesorhizobium tianshanense, contained also 4-oxo fatty acids (4-oxo-20:0, 4-oxo-i-21:0, 4-oxo-22:0). The group of amide-linked fatty acids consisted of a wide range of 3-hydroxylated and 4-oxo fatty acids whereas all the nonpolar as well as the (omega-1) hydroxylated long-chain acids and the 27-oxo-28:0 fatty acids were ester-linked. The characteristic spectrum of 3-hydroxy fatty acids and presence of 27-OH-28:0 as well as 27-oxo-28:0 acid in LPSs of Mesorhizobium showed that these strains were closely related. Therefore the lipid A fatty acid pattern could be a useful chemotaxonomic marker which helps to isolate the Mesorhizobium group from rhizobium bacteria during the classification process.

Amides↗
PubMed1999

Phylogenetic position of Mesorhizobium huakuii subsp. rengei, a symbiont of Astragalus sinicus cv. Japan.

The phylogenetic position of Rhizobium huakuii bv. renge, a symbiont of Astragalus sinicus cv. Japan (renge-sou), was studied. The following phylogenetic approaches were used: restriction fragment length polymorphism (RFLP)-polymerase chain reaction (PCR) analysis of a full-length 16S rDNA fragment, 16S rDNA analysis of the first 300-bp sequence, bacteriophage typing, and amplification of the genomic region by random primer. All the data suggest that strains of R. huakuii bv. renge should be classified into subspecies of the new genus Mesorhizobium (Jarvis et al., Inter. J. System. Bacteriol., 47, 895-898, 1997) and renamed M. huakuii subsp. rengei. All the strains fell into a tight cluster which included M. loti and M. huakuii. The strains isolated from root nodules on A. sinicus were divided into three groups as follows: group I, M. huakuii subsp. rengei B3, M. huakuii subsp. rengei My6, M. huakuii subsp. rengei My7, M. huakuii subsp. rengei My3, and M. huakuii subsp. rengei OUT30020; group II, M. huakuii subsp. huakuii CCBAU103(T), M. huakuii subsp. huakuii ACCC13005, M. huakuii subsp. huakuii 7653R, and Mesorhizobium sp. N-1; group III, Mesorhizobium sp. OUT30019. All the strains isolated in Japan except strains N-1 and OUT30019 were classified into group I. Strains in group I were sensitive to bacteriophage H1 which was isolated from rice-paddy soil in Japan. Strains in groups II and III except for M. huakuii subsp. huakuii 7653R were resistant to phage H1. Rhizobium sp. ACMP18, a native symbiont of Astragalus cicer that forms nodules on A. sinicus, showed close similarity to M. huakuii subsp. huakuii CCBAU103(T), and should thus be classified as a Mesorhizobium sp. Taken together, the results of the analyses indicate that M. huakuii subsp. rengei forms a subgroup which is distinct from M. huakuii subsp. huakuii strains isolated in China and that strain B3 is the type strain.

Journal Article↗
PubMed2002

Contrasting nifD and ribosomal gene relationships among Mesorhizobium from Lotus oroboides in northern Mexico.

PCR screens for length variation in a 5' portion of 23S ribosomal RNA and in the 3' end of the 16S rRNA-23S rRNA internal transcribed spacer (ITS) region indicated that nodule bacteria from a Mexican population of Lotus oroboides were diverse on a local scale. Three 23S rRNA length variants and five ITS length variants were detected among the 22 isolates. Sequencing of nearly full-length 16S rRNA genes in three isolates indicated that they fell into the genus Mesorhizobium, but comprised two distinct groups. Two isolates were closely related to M. loti LMG 6125T, while the other isolate clustered with an assemblage of Mesorhizobium taxa that included M. amorphae, M. plurifarium and M. huakuii. However, a phylogenetic tree based on 715 bp of the nitrogenase alpha-subunit (nifD) gene was significantly discordant with the relationships inferred from rRNA sequences. Two isolates that were nearly identical for 16S rRNA had nifD genes that varied at 2% of sites, and one of these nifD sequences was identical to that of another isolate with a strongly divergent 16S rRNA gene. A plasmid screen followed by Southern hybridization indicated that only one of these strains harbored a plasmid-borne nifD gene. These results imply that gene transfer events have altered the distribution of nifD sequences among lineages within this natural population of Mesorhizobium strains.

Alphaproteobacteria↗
PubMed1997

Phylogenetic and genetic relationships of Mesorhizobium tianshanense and related rhizobia.

The genetic and phylogenetic relationships for strains of Mesorhizobium tianshanense and its relatives were compared by an analysis of the results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of whole-cell proteins, DNA-DNA hybridization, and full 16S rRNA gene sequencing. The strains of M. tianshanense formed a cluster which was distinct from those of other rhizobium species in the clustering analysis of SDS-PAGE. DNA-DNA relatedness between A-1BS (type strain of M. tianshanense) and the type or reference strains for Mesorhizobium loti, M. huakuii, M. ciceri, M. mediterraneum, and cluster U, an unnamed rhizobial group, ranged from 4.4 to 43.8%. The phylogenetic analysis based on the 16S rRNA gene sequences showed that M. tianshanense was closely related to the Mesorhizobium phylogenetic branch and could be distinguished from the other four species in this branch. These results further confirmed that these bacteria constitute a distinct rhizobial species.

Bacterial Proteins↗
PubMed2005

Phylogenetic analysis of the genera Bradyrhizobium, Mesorhizobium, Rhizobium and Sinorhizobium on the basis of 16S rRNA gene and internally transcribed spacer region sequences.

A total of 128 strains was isolated from more than 23 legume hosts in Korea. Phylogenetic relationships between these Korean isolates and reference strains of the genera Bradyrhizobium, Mesorhizobium, Rhizobium and Sinorhizobium were analysed using their 16S rRNA gene and internally transcribed spacer (ITS) region sequences. Among the Bradyrhizobium strains, dendrograms based on both the 16S rRNA gene and ITS region sequences produced two main groups. The ITS tree yielded at least two new clusters that were discernable from the seven previously delineated genospecies. Large discrepancies were revealed between phylogenetic dendrograms based on 16S rRNA gene and ITS region sequences for members of the genus Rhizobium, reflecting their taxonomic heterogeneity. The amalgamation of Rhizobium and former members of Agrobacterium was confirmed using the 16S rRNA tree. Phylogenetic analysis of ITS region sequences showed that the Rhizobium giardinii clade (group II) and the Rhizobium radiobacter/Rhizobium rubi clade (group III) could be tentatively recognized as groups that are separable from the core group (group I), which includes Rhizobium leguminosarum. Dendrograms based on the 16S rRNA gene and ITS region sequences of Mesorhizobium strains were highly conflicting due to the poor taxonomic resolution of the 16S rRNA gene sequences and the low confidence in the ITS dendrogram. Several Korean isolates within the genus Mesorhizobium are thought to represent novel taxa when considering their relatively low ITS region sequence similarities (<80 %) to the reference strains.

Alphaproteobacteria↗
PubMed2003

Diverse Mesorhizobium plurifarium populations native to Mexican soils.

Forty-six Mesorhizobium strains associated with the leguminous plants Leucaena leucocephala and Sesbania herbacea in an uncultivated Mexican field were characterized using a polyphasic approach. The strains were identified as Mesorhizobium plurifarium based upon the close relationships with the reference strains for this species in PCR-based restriction fragment length polymorphism analyses, sequencing of 16S rRNA genes, multilocus enzyme electrophoresis, and DNA-DNA hybridization. Although the strains isolated from both plants formed the same group in multilocus enzyme electrophoresis and cross-nodulations were observed in the laboratory, different electrophoretic types were obtained from the two plants grown in natural soils, indicating the existence of a preferable association between the plants and the rhizobia. The M. plurifarium strains from Mexico and the reference strains from Africa and Brazil formed different phenotypic clusters in a numerical taxonomy. The Mexican strains did not grow at 37 degrees C and were sensitive to salty-alkaline conditions, while the reference strains from Africa and Brazil grew at 42 degrees C and were more resistant to salty-alkaline conditions. These results demonstrate that both the plants and environmental factors affected the evolution of rhizobia and that the Mexican strains had adapted to the neutral soils and the cool climate where they were isolated.

Adaptation, Biological↗
PubMed2006

Insight into the structure of Mesorhizobium loti arylamine N-acetyltransferase 2 (MLNAT2): a biochemical and computational study.

The arylamine N-acetyltransferases (NAT; EC 2.3.1.5) are xenobiotic-metabolizing enzymes (XME) that catalyze the transfer of an acetyl group from acetylCoA (Ac-CoA) to arylamine, hydrazines and their N-hydroxylated metabolites. Eukaryotes may have up to three NAT isoforms, but Mesorhizobium loti is the only prokaryote with two functional NAT isoforms (MLNAT1 and MLNAT2). The three-dimensional structure of MLNAT1 has been determined (Holton, S.J., Dairou, J., Sandy, J., Rodrigues-Lima, F., Dupret, J.M., Noble, M.E.M. and Sim, E. (2005) Structure of Mesorhizobium loti arylamine N-acetyltransferase 1. Acta Cryst, F61, 14-16). No MLNAT2 crystals have yet been produced, despite the production of sufficient quantities of pure protein. Using purified recombinant MLNAT1 and MLNAT2, we showed here that MLNAT1 was intrinsically more stable than MLNAT2. To test whether different structural features could explain these differences in intrinsic stability, we constructed a high-quality homology model for MLNAT2 based on far UV-CD data. Despite low levels of sequence identity with other prokaryotic NAT enzymes ( approximately 28% identity), this model suggests that MLNAT2 adopts the characteristic three-domain NAT fold. More importantly, molecular dynamics simulations on the structures of MLNAT1 and MLNAT2 suggested that MLNAT2 was less stable than MLNAT1 due to differences in amino-acid sequence/structure features in the alpha/beta lid domain.

Amino Acid Sequence↗
PubMed2000

Efficient transformation of Mesorhizobium huakuii subsp. rengei and Rhizobium species.

The transformation of Mesorhizobium huakuii subsp. rengei B3 with either pBBR122 or pKT230 was carried out. We determined the optimal conditions required for transformation by electroporation and obtained up to 10(5) CFU/microg pBBR122. Plasmids prepared from strain B3 yielded higher transformation efficiency than those from various dam or dcm mutant strains of Escherichia coli. This result suggests that a high transformation efficiency is not related to the methylation of plasmid DNA in E. coli. Using the optimal conditions for electroporation, we performed transformation of several species of Rhizobium, Mesorhizobium and Sinorhizobium. All tested strains of these species were transformed with pBBR122. Strains of M. huakuii and R. phaseoli AHU1133 were transformed at high efficiency, whereas transformation efficiencies of Rhizobium sp. NGR234 and S. meliloti strains were less than 2 x 10(3) CFU/microg plasmid DNA.

Journal Article↗
PubMed2001

Effects of salinity on protein and lipopolysaccharide pattern in a salt-tolerant strain of Mesorhizobium ciceri.

AIMS: To characterize the physiological and metabolic responses of Mesorhizobium ciceri strain ch-191 to salt stress, investigating the changes induced by salinity in protein and lipopolysaccharide profiles, as well as determining the accumulation of amino acids, glutamate and proline. METHODS AND RESULTS: Strain ch-191 of M. ciceri was grown with different NaCl concentrations. Protein and lipopolysaccharide patterns were determined by electrophoresis. The strain ch-191 tolerated up to 200 mmol l-1 NaCl, although higher salt dosages limited its growth and induced changes in the protein profile. The most noteworthy change in the LPS-I pattern was the decrease in the slowest band and the appearance of an intermediate mobility band. The accumulation of proline in response to salt stress surpassed that of glutamate. CONCLUSION: The protein profile showed major alterations at salinity levels which inhibited growth. However, the alterations in the LPS profile and accumulation of compatible solutes were evident from the lowest levels, suggesting that these changes may constitute adaptative responses to salt, allowing normal growth. SIGNIFICANCE AND IMPACT OF THE STUDY: The selection and characterization of salt-tolerant strains, which also show efficient symbiotic performance under salinity, may constitute a strategy for improving Cicer arietinum-Mesorhizobium ciceri symbiosis in adverse environments.

Bacterial Proteins↗
PubMed2002

Analysis of phospholipids and ornithine-containing lipids from Mesorhizobium spp.

Polar lipid compositions of seven strains belonging to the four species of the Mesorhizobium genus were described. The lipid patterns of Mesorhizobium strains were very similar. Only quantitative differences were observed. Diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and phosphatidylcholine (PC) were found to be the major phospholipids of the analysed bacteria. In addition, two methylated derivatives of PE were observed: phosphatidyl-N,N-dimethylethanolamine (DMPE) and phosphatidyl-N-monomethylethanolamine (MMPE). Polar head groups of those phospholipids were predominately acylated with lactobacillic (19:0 cyclopropane) acid. Ornithine-containing lipid (OL) was also identified. 3-hydroxy fatty acids found in the lipid preparations were derived exclusively from the ornithine lipid. 3-hydroxylactobacillic was the main acyl residue amide linked to the ornithine.

Alphaproteobacteria↗
PubMed2002

Rapid colorimetric quantification of lipo-chitooligosaccharides from Mesorhizobium loti and Sinorhizobium meliloti.

Nod factors are lipids with a chitinlike headgroup produced by gram-negative Rhizobium bacteria. These lipo-chitooligosaccharides (LCOs) are essential signaling molecules for accomplishing symbiosis between the bacteria and roots of legume plants. Despite their important role in the Rhizobium-legume interaction, no fast and sensitive Nod factor quantification methods exist. Here, we report two different quantification methods. The first is based on the enzymatic hydrolysis of Nod factors to release N-acetylglucosamine (GlcNAc), which can subsequently be quantified. It is shown that the degrading enzyme, glusulase, releases exactly two GlcNAc units per pentameric nodulation factor from Mesorhizobium loti factor, allowing quantification of LCOs from Mesorhizobium loti. The second method is based on a specific type of Nod factors that are sulfated on the reducing GlcNAc, allowing quantification analogous to the quantification of sulfolipids. Here, a two-phase extraction method is used in the presence of methylene blue, which specifically forms an ion pair with sulfated lipids. The blue ion pair partitions into the organic phase, after which the methylene blue signal can be quantified. To enable Nod factor quantification with this method, the organic phase was modified and the partitioning was evaluated using fluorescent and radiolabeled sulfated Nod factors. It is shown that sulfated LCOs can be quantified with this method, using sodium dodecyl sulfate for calibration. Both methods allow Nod factor quantification in parallel enabling a fast and easy detection of nanomole quantities of Nod factors. Accurate Nod factor quantification will be crucial for characterization and cross-comparison of the affinity for Nod factors of newly identified Nod factor binding proteins or putative Nod factor receptors.

Acetylglucosamine↗
PubMed1998

Characterization of tropical tree rhizobia and description of Mesorhizobium plurifarium sp. nov.

A collection of strains isolated from root nodules of Acacia species in Senegal was analysed previously by electrophoresis of total cell protein, auxanographic tests, rRNA-DNA hydridization, 16S rRNA gene sequencing, DNA base composition and DNA-DNA hybridization [de Lajudie, P., Willems, A., Pot, B. & 7 other authors (1994). Int J Syst Bacteriol 44, 715-733]. Strains from Acacia were shown to belong to two groups, Sinorhizobium terangae, and a so-called gel electrophoretic cluster U, which also included some reference strains from Brazil. Further taxonomic characterization of this group using the same techniques plus repetitive extragenic palindromic-PCR and nodulation tests is presented in this paper. Reference strains from Sudan and a number of new rhizobia isolated from nodules of Acacia senegal, Acacia tortilis subsp. raddiana and Prosopis juliflora in Senegal were included. As a result of this polyphasic approach, the creation of a new species, Mesorhizobium plurifarium, is proposed for a genotypically and phenotypically distinct group corresponding to the former cluster U and containing strains isolated from Acacia, Leucaena, Prosopis and Chamaecrista in West Africa (Senegal), East Africa (Sudan) and South America (Brazil). The type strain of Mesorhizobium plurifarium ORS 1032 has been deposited in the LMG collection as LMG 11892.

Acacia↗
PubMed1999

Diversity of rhizobia associated with Amorpha fruticosa isolated from Chinese soils and description of Mesorhizobium amorphae sp. nov.

Fifty-five Chinese isolates from nodules of Amorpha fruticosa were characterized and compared with the type strains of the species and genera of bacteria which form nitrogen-fixing symbioses with leguminous host plants. A polyphasic approach, which included RFLP of PCR-amplified 16S rRNA genes, multilocus enzyme electrophoresis (MLEE), DNA-DNA hybridization, 16S rRNA gene sequencing, electrophoretic plasmid profiles, cross-nodulation and a phenotypic study, was used in the comparative analysis. The isolates originated from several different sites in China and they varied in their phenotypic and genetic characteristics. The majority of the isolates had moderate to slow growth rates, produced acid on YMA and harboured a 930 kb symbiotic plasmid (pSym). Five different RFLP patterns were identified among the 16S rRNA genes of all the isolates. Isolates grouped by PCR-RFLP of the 16S rRNA genes were also separated into groups by variation in MLEE profiles and by DNA-DNA hybridization. A representative isolate from each of these DNA homology groups had a separate position in a phylogenetic tree as determined from sequencing analysis of the 16S rRNA genes. A new species, Mesorhizobium amorphae, is proposed for the majority of the isolates, which belonged to a moderately slow- to slow-growing, acid-producing group based upon their distinct phylogenetic position, their unique electrophoretic type, their low DNA homology with reference strains representing the species within the genus Mesorhizobium and their distinct phenotypic features. Strain ACCC 19665 was chosen as the type strain for M. amorphae sp. nov.

Base Composition↗