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At least 19 recordsLinked to original sources
PubMed1976

Discrimination of Rhizobium japonicum, Rhizobium lupini, Rhizobium trifolii, Rhizobium leguminosarum and of bacteroids by uptake of 2-ketoglutaric acid, glutamic acid and phosphate.

Rhizobium strains (one each of Rh. japonicum, Rh. lupini, Rh. leguminosarum) take up 2-ketoglutaric acid in general much faster and from lower concentrations in the medium than strains of Escherichia coli, Bacillus subtilis and Chromobacterium violaceum. A strain of Enterobacter aerogenes, however, is more similar to some Rhizobium strains. The same strains of Rhizobium take up also phosphate much faster and from lower concentrations than the other bacteria tested. 4 strains of Rh. lupini proved to be significantly different from 4 strains of Rh. trifolii in taking up L-glutamic acid from three to ten times lower concentration within 5 h. A similar difference was noticed between 5 strains of Rh. leguminosarum and 2 strains of Rh. japonicum for the uptake of 2-ketoglutaric acid and of L-glutamic acid. Isolated bacteroids from nodules of Glycine max var. Chippeway have a reduced uptake capacity for glutamic acid and for 2-ketoglutaric acid during the first 10-12 h, but reach the same value after 24 h as free living Rh. japonicum cells. The differences in the uptake kinetics are independent of cell concentration. The group II Rhizobium strains (Rh. japonicum and Rh. lupini, slow growing Rhizobium) are characterized by a rapid uptake of glutamic acid to a low remaining concentration of 1-3 X 10(-7) M and an uptake of 2-ketoglutaric acid to a remaining concentration of 2-5 X 10(-7) M. The group I Rhizobium strains (Rh. trifolii and Rh. leguminosarum, fast growing Rhizobium), can be characterized by a much slower uptake of both substances with a more than ten times higher concentration of both metabolites remaining in the medium after the same time.

Bacillus subtilis↗
PubMed2026

Rhizobium zaerense sp. nov., a novel member of the Rhizobium leguminosarum species complex with a broad geographic distribution and multiple legume hosts.

A novel nitrogen-fixing rhizobial strain, designated Z1P35ᵀ, was isolated from root nodules of Pisum sativum grown in the Zaër region of Morocco. Phylogenetic analysis of the 16S rRNA gene placed strain Z1P35ᵀ within the genus Rhizobium, showing 100% sequence identity with several undescribed genospecies of the Rhizobium leguminosarum species complex (Rlc). Strain Z1P35ᵀ exhibited low average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values with all described Rhizobium species, but high ANI and dDDH values (97.62 and 78.8%, respectively) with Rhizobium sp. SRDI565, representing genospecies M (GsM) of the Rlc, suggesting that Z1P35ᵀ represents a novel species corresponding to GsM within this complex. FastANI screening against all Rhizobium genomes available in GenBank revealed that Z1P35ᵀ shares ANI values above the bacterial species delimitation threshold with 17 unclassified strains, which, together with Z1P35ᵀ and Rhizobium sp. SRDI565 (GsM), form a distinct lineage within the Rlc. These 17 strains originate from root nodules of diverse legume hosts and are distributed across the Mediterranean region and Australia, including representatives of the symbiovars viciae and trifolii. Phylogenomic analysis further confirms the clustering of Z1P35ᵀ with Rhizobium sp. SRDI565 (GsM) and several undescribed Rhizobium strains, forming a unique taxonomic unit clearly distinct from other members of the Rlc. Strain Z1P35ᵀ has a genome of 7.6 Mb with a G+C content of 61 mol% and carries numerous genes associated with chemotaxis, nodulation, nitrogen fixation, phosphate solubilization, iron acquisition and abiotic stress tolerance. Differentiation of Z1P35ᵀ from described Rhizobium species was further supported by phenotypic and chemotaxonomic analyses. Based on these results, we conclude that Z1P35T belongs to a novel species, corresponding to genospecies M within the Rlc, for which we propose the name Rhizobium zaerense sp. nov. The type strain is Z1P35ᵀ (DSM 120601ᵀ=CCMM B1365ᵀ).

Phylogeny↗
PubMedDate not supplied

[Nitrogenase activity of Rhizobium meliloti and Rhizobium vigna in a root tisse culture of leguminous and nonleguminous plants].

As was shown using the acetylene technique, the nitrogenase activity of Rhizobium meliloti and Rhizobium vigna increased when they were cultivated with the root tissue cultures of legumes (lucerne, sweetclover) and non-legumes (tobacco, glasswort, carrot), particularly in the case of the former. The maximum activity of nitrogenase was found in R. meliloti. The tissue cultures of legumes had no effect on the growth of Rhizobium whereas the tissues of non-legumes stimulated their biomass accumulation though the activity of nitrogenase in both Rhizobium cultures was low in this case. Therefore, the metabolites of legumes produced a specific action on the nitrogenase of nodule bacteria.

Culture Media↗
PubMed1978

Genetically marked Rhizobium identifiable as inoculum strain in nodules of soybean plants grown in fields populated with Rhizobium japonicum.

The fate of an inoculum strain of Rhizobium japonicum was studied using a genetically marked strain I-11O subline carrying resistance markers for azide, rifampin, and streptomycin (I-110 ARS). At the time of planting into a field populated with R. japonicum, seeds of soybean cultivars Kent and Peking were inoculated with varying cell densities of strain I-110 ARS. At various times during the growing season, surface-sterilized root nodules were examined for the presence of the inoculum strain by plating onto selective media. The recovery of the inoculum strain was unambiguous, varying, in the case of Kent cultivar, from about 5% with plants (sampled at 51 days) that had been inoculated with 3 X 10(8) cells per cm of row to about 20% with plants (sampled at 90 days) that had been inoculated with 3 X 10(9) cells per cm. The symbiotically incompatible interaction of Peking and strain 110 in Rhizobium-populated field soil was confirmed by the finding that at 60 days after planting, only one nodule in 360 sampled contained strain I-110 ARS. The use of genetically marked Rhizobium bacteria was found to provide for precise identification of the inoculum strain in nodules of field-grown soybeans.

Azides↗
PubMed1977

Flow-microfluorometric analysis of Escherichia coli, Rhizobium meliloti, and Rhizobium japonicum at different stages of the growth cycle.

The applicability of flow-microfluorometry (FMF) to the study of bacterial samples was investigated on cultures of Rhizobium meliloti, Rhizobium japonicum, and Escherichia coli using fluorescent and light-scattering signals. This technique which analyzes individual bacterial cells in a population was used to monitor the relative change in nucleic acid content and cell size during the growth cycle of the three microorganisms which were known to have different growth rates. Early log-phase E. coli cells contained at least eightfold more nucleic acid and were significantly larger than the stationary-phase cells. Cultures of early log-phase R. meliloti cells contained three to four-fold more nucleic acid and were slightly larger than cells in the stationary phase. Rhizobium japonicum had very little change in either parameter. In general, the amount of change in both cell size and nucleic acid content upon initiation of log-phase growth was related to the overall growt rate of the organisms, with E. coli experiencing the greatest change and R. japonicum the least. Results obtained by FMF analysis, therefore, were consistent with observations reported by earlier workers. Cultures of R. meliloti also were used to demonstrate that the intensity of the fluorescent signals was sensitive to digestion by DNase and RNase and to prolonged storage and fixation. The potential use of FMF in the study of microorganisms is discussed.

Cell Cycle↗
PubMed1977

Differential stimulation and inhibition of growth of Rhizobium trifolii strain T1 and other Rhizobium species by various carbon sources.

The physiological properties of Rhizobium trifolii strain T1 were studied in detail, since this strain has many useful characteristics and appears ideal for development as a reference strain for R. trifolii. Some tricarboxylic acid cycle intermediates and related compounds were found to stimulate growth in the presence of sucrose and arabinose, while others inhibited growth partially or completely. Other R. trifolii strains behaved likewise. Moreover, similar responses were also observed with other Rhizobium species, both fast-growing and slow-growing. On the basis of these growth responses, the various species of fast-growing and slow-growing rhizobia could be differentiated. Of the fast-growers tested, R. trifolii and R. leguminosarum are much more closely related to each other than either is to R. meliloti. Similarly, the slow-growing cowpea rhizobia are more closely related to R. japonicum than either group is to R. lupini. It is proposed that strain T1 should be developed as the reference strain for Rhizobium trifolii.

Arabinose↗
PubMed1977

Regulation of nitrogen fixation in Rhizobium spp. Isolation of mutants of Rhizobium trifolii which induce nitrogenase activity.

This communication describes the isolation and characterization of mutants of Rhizobium trifolii which can induce nitrogenase activity in defined liquid medium. Two procedures were used for the isolation of these mutants from R. trifolii strain DT-6: (1) following chemical mutagenesis, slow growing mutants were selected which were unable to utilize NH+4 as sole source of nitrogen; (2) as spontaneous mutants resistant to the glutamate analogue L-methionine-DL-sulfoximine. Mutants (DT-71, DT-125) isolated by these procedures induced nitrogenase activity in the free-living state, whereas the parent strain lacked this property. Induction of nitrogenase activity in these mutants occurred during the late exponential phase of growth when the rate of protein synthesis was decreasing. The addition of NH+4 to a medium containing glutamate as the nitrogen-source resulted in a 50--70% reduction (repression?) of nitrogenase activity; in contrast, the rate of protein synthesis or the rate of respiration was not influenced by exogenous NH+4. Biochemical analysis showed that these mutants (strains DT-71 and DT-125) have defects in both nitrogen and carbon metabolism. The levels of glutamate synthase (both NADP+ -and NAD+ -dependent activities) and glutamate dehydrogenase (NAD+-dependent activity) were markedly lower. In addition, the mutants were found to have no detectable ribitol dehydrogenase or beta-galactosidase activity. These findings are discussed in relation to a mechanism of regulation of symbiotic nitrogen fixation.

Ammonia↗
PubMedDate not supplied

Action of metabolites of isolated plant tissues on the nitrogenase activity of Rhizobium vigna and Rhizobium meliloti.

The dependence of the nitrogenase activity of Rhizobium meliloti on the strain peculiarities of the cultures, the composition of the media used, and the metabolites of legume tissue cultures was demonstrated by the acetylene method. The nitrogenase activity is significantly higher in R. vigna than in R. meliloti, under the same experimental conditions. Enrichment of the Murashige-Skoog medium with arabinose (25 mM), succinate (25 mM), glutamine (2 mM nitrogen), and yeast extract (0.1%) substantially stimulated the nitrogenase activity of a pure culture of R. vigna. The maximum nitrogenase activity on this medium was noted when metabolites of sweet clover tissue were introduced.

Ethylenes↗
PubMed1975

Studies on phage 1P receptors in Rhizobium trifolii and Rhizobium leguminosarum.

The rate of phage 1P attachment to Rhizobium cell walls was increased in the presence of ethylenediaminetetraacetic acid (EDTA). On the other hand the rate of adsorption of phage 1P to the Triton -- insoluble cell walls was diminished. The subsequent treatment of cell walls with 2% Triton X-100 and 5mM EDTA caused a more substantial decline of the phage inactivating capacity. Lipopolysaccharides (LPS) isolated from the sensitive strains, contrary to those from phage-resistant mutants, inactivated effectively phage 1P. The content of sugars in LPS preparations was determined by using gas liquid chromatography.

Adsorption↗
PubMed1975

Fructose 1,6-bisphosphate aldolase activity of Rhizobium species.

FDP aldolase was found to be present in the cell-free extracts of Rhizobium leguminosarum, Rhizobium phaseoli, Rhizobium trifolii, Rhizobium meliloti, Rhizobium lupini, Rhizobium japonicum and Rhizobium species from Arachis hypogaea and Sesbania cannabina. The enzyme in 3 representative species has optimal activity at pH 8.4 in 0.2M veronal buffer. The enzyme activity was completely lost by treatment at 60 degrees C for 15 min. The Km values were in the range from 2.38 to 4.55 X 10(-6)M FDP. Metal chelating agents inhibited enzyme activity, but monovalent or bivalent metal ions failed to stimulate the activity. Bivalent metal ions in general were rather inhibitory.

Cell-Free System↗
PubMedDate not supplied

Isolation and characterization of Rhizobium (IC3342) genes that determine leaf curl induction in pigeon pea.

Nodulation by the Rhizobium strain IC3342 causes a leaf curl syndrome in certain tropical legumes such as pigeon pea (Cajanus cajan) (N.M. Upadhyaya, J.V.D.K. Kumar Rao, D.S. Letham, and P.J. Dart, Physiological and Molecular Plant Pathology 39:357-373, 1991). Transposon (Tn5) mutagenesis of this leaf curl-inducing (Curl+) Rhizobium strain yielded two Curl- Fix- and three Curl- Fix+ mutants. Plasmid visualization and subsequent Southern blot hybridization analyses with Tn5, nif and nod gene probes showed that the Tn5 element had inserted into the symbiotic (Sym) plasmid in three of the mutants. Restriction endonuclease analyses indicated that none of the Tn5 insertions were closely linked. Tn5-containing EcoRI fragments were cloned from each mutant and used as probes to isolate the corresponding wild-type DNA fragments from a cosmid (pLAFR3) genomic library. Fix+ and/or Curl+ phenotypes were restored in each mutant by the introduction of cosmids containing the corresponding wild-type DNA. A closely related but Curl- Rhizobium strain ANU240 was shown, by Southern hybridization, to contain conserved DNA sequences of all but one of the identified genetic regions of the Curl+ Rhizobium strain IC3342. Cosmids containing the genetic region unique to the strain IC3342, designated lcr1, conferred a Curl+ phenotype on the strain ANU240. DNA sequence analysis of the cloned lcr1 region revealed five open reading frames (ORFs). The ORF2 showed homology with the Escherichia coli regulatory gene ompR, and ORF4 showed homology with E. coli and Rhizobium meliloti regulatory genes fnr and fixK, respectively.

Amino Acid Sequence↗
PubMed1978

Control of ammonium assimilation in Rhizobium 32H1.

The symbiotic, nitrogen-fixing bacterium Rhizobium sp. 32H1 is a specialized ammonium producer during symbiosis. However, during free-living growth, Rhizobium 32H1 assimilates ammonium very poorly. Two pathways of ammonium assimilation exist in enteric bacteria. One is mediated by glutamate dehydrogenase, and the other is mediated by glutamine synthetase-glutamate synthase. The former pathway is altogether inoperative in Rhizobium 32H1; the latter pathway operates at a slow rate and is under strict negative control by ammonium itself. Rhizobium 32H1 glutamine synthetase activity is modulated by both repression-derepression and reversible adenylylation. For a biochemical process lacking an alternative pathway, such a regulatory pattern exacerbates the very process. This suggests that Rhizobium 32H1 restricts its own ammonium assimilation to maximize the contribution of fixed nitrogen to the host plant during symbiosis.

Adenine Nucleotides↗
PubMed1979

Structure of nitrogen-fixing nodules formed by Rhizobium on roots of Parasponia andersonii Planch.

The structure of nitrogen-fixing nodules produced by Rhizobium infection of the non-legume Parasponia andersonii was examined by light and electron (both SEM and TEM) microscopy. Comparisons were made with the nodules previously described on P. rugosa. Like the nodules on different non-legumes formed by other types of endophytes, the Rhizobium nodules on Parasponia resembled modified roots by having a central vascular bundle surrounded by an endophyte-infected zone. The intimate association between the Rhizobium and the host nodule cell was compared with the Rhizobium association found in legumes. The rhizobia were not released from the infection thread as happens in the legume. The infection thread, which propagates the Rhizobium infection to new cells, was transformed within a nodule cell from a darkly stained (light microscopy) or very electron-dense (TEM) structure to a number of thread types. The walls of the threads varied greatly in thickness and often the thread structures were without rigid walls and were only enclosed by a plasma membrane. If the rhizobia are transformed into bacteroids, as in the legumes, it would have to occur when the threads had reached their mature size, when bacterial division had ceased. Nitrogen fixation was considered to occur in all thread types.

Nitrogen Fixation↗
PubMed1979

Polypeptide synthesis by Rhizobium bacteroids and bacteria.

When Rhizobium bacteroids (strain NZP 2257) from lupin nodules were isolated and incubated aerobically at high osmolarity, they incorporated [35S]-methionine into a characteristic set of polypeptides; many of these polypeptides coelectrophoresed on SDS-polyacrylamide gels with the bacteroid polypeptide bands stained by Coomassie blue. The labelled polypeptides were stable for several hours in pulse-chase experiments. Changes in the concentration of H+, K+ and Mg2+ in the incubation mixture affected overall incorporation of label, but not the relative incorporation into different polypeptides. A similar set of bacteroid polypeptides was labelled in situ when detached nodules were fed [35S]methionine. Distinctive labelling patterns were observed with bacteroid suspensions from mature and immature nodules, with a transitional pattern at the time when nitrogenase activity appeared. Two of the major labelled components in mature bacteroids had estimated molecular weights of 60- and 34-kilodaltons similar to values reported by others for the constituent polypeptides of nitrogenase. Bacteroids of the same Rhizobium strain grown in different plant hosts gave similar polypeptide labelling patterns in purified suspensions, but bacteroids of different Rhizobium strains gave different patterns. The polypeptide labelling patterns obtained using broth-cultured Rhizobium bacteria from various growth stages and growth media differed from those obtained using bacteroids of the same strain.

Bacteria↗
PubMed1978

Transformation of Azotobacter vinelandii strains unable to fix nitrogen with Rhizobium spp. DNA.

The phenotypes of Azotobacter vinelandii ATCC 12837 strains defective in nitrogen fixation (Nif-) were characterized by intrageneric transformation with known Nif- strains of A. vinelandii OP. These former mutant strains were used as recipients for intergeneric transformation by deoxyribonucleic acid (DNA) prepared from Rhizobium spp. to determine if the rhizobia would transform the Azotobacter Nif- phenotypes to Nif+. The frequency of Nif+ transformants using Rhizobium DNA was always less than the frequency using Azotobacter wild-type DNA but was greater than the spontaneous reversion frequency. The Azotobacter Nif+ recombinants also were stable. DNA from all of the Rhizobium spp. transformed to Nif+ Azotobacter mutants defective in the nitrogenase component I (molybdoferredoxin); however, some recombinants had a lower nitrogenase activity and a delayed nitrogenase depression time. Mutants defective in the pleiotrophic transcriptional control of both nitrogenase components were transformed to Nif+ by the asymbiotic nitrogen fixing Rhizobium sp. 32H1 and 41A1, but not the symbiotic nitrogen-fixing species. The significance of these results and the possible future applications of this system are discussed.

Azotobacter↗
PubMed1978

Rhizobium strain identification in Arachis hypogaea nodules by enzyme-linked immunosorbent assay (ELISA).

The technique of enzyme-linked immunosorbent assay (ELISA) was used for serological identification of peanut Rhizobium strains both in cell suspension of pure culture and in single root nodules of groundnut (Arachis hypogaea) plants. Antisera of three peanut Rhizobium strains were tested against eight different Rhizobium isolates. Three serogroups identified by agglutination and immunodiffusion tests were confirmed by ELISA. In this experiment ELISA was more sensitive by four to six orders of magnitude than the agglutination and immunodiffusion tests and enabled the detection of Rhizobium antigens in cell suspensions of 10(4)-10(5) cells per millilitre. The reactions of culture and nodule antigens were identical for all strains investigated. ELISA enabled the precise typing of rhizobial isolates in single small root nodules. The minimum fresh weight of nodule tissue necessary to perform the ELISA test was 0.4 mg crushed in 1 ml of phosphate-buffered saline (PBS). ELISA was also successfully used for strain identification in mixed inoculated plants. One of the strains in each pair formed most of the nodules examined.

Antigens, Bacterial↗