Characterisation of dry and mucoid colonies isolated from Australian rhizobial inoculant strains for Medicago species

2005 ◽  
Vol 45 (3) ◽  
pp. 151 ◽  
Author(s):  
A. McInnes ◽  
P. Holford ◽  
J. E. Thies
Keyword(s):  
Nitrogen Fixation ◽  
Sinorhizobium Meliloti ◽  
Dry Weight ◽  
Sequence Element ◽  
Shoot Dry Weight ◽  
Single Colony ◽  
Agar Media ◽  
Fixation Capacity ◽  
Medicago Species ◽  
K Antigen

The presence of dry and mucoid colonies in cultures of rhizobial strains used in the production of commercial Australian inoculants is of concern for quality assurance because of the possibility of altered capacity for nodulation and nitrogen fixation by the different colony types. In this study, single colony isolates obtained from dry and mucoid colonies present in commercial cultures of Sinorhizobium meliloti were investigated to identify stability in culture, genetic identity and changes in exopolysaccharide (EPS) production, nodulation and nitrogen fixation. The 2 strains studied were WSM688 and WSM826 (Australian inoculant strains for annual and perennial medics, respectively), both of which produced only mucoid colonies on agar media when originally isolated from nodules. Dry and mucoid single colony isolates from the ‘mother cultures’ of the 2 strains exhibited stable colony phenotypes during successive subculturing in our laboratory and were shown to be most closely related to S. meliloti using 16S rRNA partial sequencing. All isolates produced at least 1 of 3 exopolysaccharides (succinoglycan, EPS II and K antigen) that are required for successful nodulation of Medicago species by S. meliloti strains, as indicated by nodulation of host legumes. Strain WSM826 isolates probably produce succinoglycan, as shown by similarity to the succinoglycan-producing strain Rm1021 in a calcofluor binding assay. In contrast to published work, there was no evidence that loss of mucoidy in dry colony isolates of either strain was associated with the presence of an insertion sequence element in the expR gene that inhibits EPS II production. For strain WSM688, dry and mucoid isolates were identical by PCR fingerprinting and showed a similar capacity to nodulate and fix nitrogen with the target host legume M. truncatula in glasshouse tests. In contrast, strain WSM826 mucoid isolates produced PCR fingerprints that were different from each other and from the WSM826 dry colony isolates. Dry and mucoid colonies may have arisen from substantial genetic change or through contamination of cultures by other S. meliloti strains. One WSM826 mucoid isolate (826-3) produced significantly lower shoot dry weight when inoculated onto both the target host M. sativa and non-target host M. truncatula, even though the capacity to nodulate both hosts was retained. This suggests that this isolate was affected in its nitrogen fixation capacity. Further research is required to identify the origin and extent of colony variation in commercial S. meliloti cultures.

scholarly journals Mutation in the ntrR Gene, a Member of the vap Gene Family, Increases the Symbiotic Efficiency of Sinorhizobium meliloti

2001 ◽  
Vol 14 (7) ◽  
pp. 887-894 ◽  
Author(s):  
Boglárka Oláh ◽  
Erno Kiss ◽  
Zoltán Györgypál ◽  
Judit Borzi ◽  
Gyöngyi Cinege ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pathogenic Bacteria ◽  
Sinorhizobium Meliloti ◽  
Root Nodules ◽  
Nifh Gene ◽  
Dry Weight ◽  
Nodule Occupancy ◽  
Gene Encoding ◽  
Symbiotic Efficiency ◽  
Host Interactions

In specific plant organs, namely the root nodules of alfalfa, fixed nitrogen (ammonia) produced by the symbiotic partner Sinorhizobium meliloti supports the growth of the host plant in nitrogen-depleted environment. Here, we report that a derivative of S. meliloti carrying a mutation in the chromosomal ntrR gene induced nodules with enhanced nitrogen fixation capacity, resulting in an increased dry weight and nitrogen content of alfalfa. The efficient nitrogen fixation is a result of the higher expression level of the nifH gene, encoding one of the subunits of the nitrogenase enzyme, and nifA, the transcriptional regulator of the nif operon. The ntrR gene, controlled negatively by its own product and positively by the symbiotic regulator syrM, is expressed in the same zone of nodules as the nif genes. As a result of the nitrogen-tolerant phenotype of the strain, the beneficial effect of the mutation on efficiency is not abolished in the presence of the exogenous nitrogen source. The ntrR mutant is highly competitive in nodule occupancy compared with the wild-type strain. Sequence analysis of the mutant region revealed a new cluster of genes, termed the “ntrPR operon,” which is highly homologous to a group of vap-related genes of various pathogenic bacteria that are presumably implicated in bacterium-host interactions. On the basis of its favorable properties, the strain is a good candidate for future agricultural utilization.

scholarly journals The Root Endophytic Fungus Serendipita indica Decreased the Phytotoxicity of Zinc Oxide Nanoparticles to Alfalfa (Medicago sativa L.)

2021 ◽  
Author(s):  
Leila Tabande ◽  
Mozhgan Sepehri ◽  
Jafar Yasrebi ◽  
Mehdi Zarei ◽  
Reza Ghasemi-Fasaei ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Plant Growth ◽  
Zinc Oxide Nanoparticles ◽  
Sinorhizobium Meliloti ◽  
Dry Weight ◽  
Oxide Nanoparticles ◽  
Zno Nps ◽  
Shoot Dry Weight ◽  
Nano Zinc Oxide ◽  
Nano Zinc

Abstract Zinc oxide nanoparticles (ZnO-NPs) are among the most commonly used nano-fertilizers (NF). However, elevated levels of ZnO-NPs in soil may affect plant growth and development due to its potential toxicity when accumulated in large amounts in plant tissues. This research was conducted using an in situ rhizobox system with the aims of evaluating Zinc uptake from nano-zinc oxide amended rhizosphere soil by alfalfa plant and the effect of plant growth promoting microorganisms on alleviating the phytotoxicity of ZnO-NPs. Treatments included microbial inoculations (Sinorhizobium meliloti, Serendipita indica) and different ZnO-NPs concentrations (0, 400 and 800 mg Kg− 1) with three replications. The results indicated that S. indica minimized the phytotoxicity of ZnO-NPs to alfalfa by enhancing growth rate and decreasing Zinc (Zn) translocation from root to shoot. Compared with plants inoculated with S. meliloti, co-inoculation with S. indica increased the shoot dry weight by 18.33% and 8.05% at 400 and 800 mg Kg− 1ZnO-NPs. However, at the highest level of ZnO-NPs (800 mg kg− 1), root inoculation of S. indica and S. indica + S. meliloti decreased Zn transfer factor by 60.2% and 44.3% compared to S. meliloti, respectively. Furthermore, a distinct relation between tolerance of S. indica-colonized plant to ZnO-NPs and the ability of S. indica in inhibiting or retarding degradation of polyunsaturated lipids through prevention of excess reactive oxygen species formation was observed. Malondialdehyde content of inoculated plants with S. indica either alone or in combination with S. meliloti was significantly lower than non-inoculated plants (p < 0.01). Zn-induced oxidative stress was mitigated by S. indica through enhanced activities of catalase and peroxidase enzymes. The findings of the present study indicate the potential use of endophytes fungus S. indica for ensuring food safety and security, and human health in heavy metal–polluted soil by reducing the phytoavailability of heavy metals in the aerial parts of the host plants.

scholarly journals Influence of the Poly-3-Hydroxybutyrate (PHB) Granule-Associated Proteins (PhaP1 and PhaP2) on PHB Accumulation and Symbiotic Nitrogen Fixation in Sinorhizobium meliloti Rm1021

2007 ◽  
Vol 189 (24) ◽  
pp. 9050-9056 ◽  
Author(s):  
Chunxia Wang ◽  
Xiaoyan Sheng ◽  
Raymie C. Equi ◽  
Maria A. Trainer ◽  
Trevor C. Charles ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Sinorhizobium Meliloti ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Dry Weight ◽  
Granule Formation ◽  
Maldi Tof ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity ◽  
Associated Proteins

ABSTRACT Sinorhizobium meliloti cells store excess carbon as intracellular poly-3-hydroxybutyrate (PHB) granules that assist survival under fluctuating nutritional conditions. PHB granule-associated proteins (phasins) are proposed to regulate PHB synthesis and granule formation. Although the enzymology and genetics of PHB metabolism in S. meliloti have been well characterized, phasins have not yet been described for this organism. Comparison of the protein profiles of the wild type and a PHB synthesis mutant revealed two major proteins absent from the mutant. These were identified by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) as being encoded by the SMc00777 (phaP1) and SMc02111 (phaP2) genes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins associated with PHB granules followed by MALDI-TOF confirmed that PhaP1 and PhaP2 were the two major phasins. Double mutants were defective in PHB production, while single mutants still produced PHB, and unlike PHB synthesis mutants that have reduced exopolysaccharide, the double mutants had higher exopolysaccharide levels. Medicago truncatula plants inoculated with the double mutant exhibited reduced shoot dry weight (SDW), although there was no corresponding reduction in nitrogen fixation activity. Whether the phasins are involved in a metabolic regulatory response or whether the reduced SDW is due to a reduction in assimilation of fixed nitrogen rather than a reduction in nitrogen fixation activity remains to be established.

scholarly journals EVALUATION OF SEVERAL GROWING MEDIA FOR USE IN NITROGEN FIXATION RESEARCH

HortScience ◽  
1992 ◽  
Vol 27 (11) ◽  
pp. 1166b-1166
Author(s):  
Stephanie Rademan ◽  
Dyremple Marsh
Keyword(s):  
Nitrogen Fixation ◽  
Seed Coat ◽  
Germination Rate ◽  
Dry Weight ◽  
Kidney Bean ◽  
Nodule Development ◽  
Growing Media ◽  
Shoot Dry Weight ◽  
Gm Plants ◽  
Wide Range

A wide range of methodologies, ranging from Leonard jar to growth pouch have been used to investigate the nitrogen fixation process in leguminous crops. The effectiveness of most of these research methods have been questioned. Problems encountered vary from difficulty in root separation to water log conditions. This study was undertaken to determine the effect of different growing media on nodule development and harvestability. Black and Red seed coat kidney bean were surface sterilized and inoculated with the Rhizobium phaseoli strain UMR 1899. Seeds were planted in 8.5 cm diameter sterile clay pots containing the respective growing medium. These growing media were sand, Promix GM, Promix BX, and fritted clay. The black seed coat kidney bean had higher germination rate under all media for all dates recorded. Black kidney bean grown in sand and fritted clay had plant heights significantly greater than ones grown in the other media on the third harvest date. Nodule activities as measured by shoot dry weight and nodule number were significantly higher in both beans grown in fritted clay than in other media. Promix GM plants with dry weight of .45g for the black bean and .32g for the red beans were the lowest. Nodule separation from the growing media was easiest when plants were grown in sand, however, this was not significantly different from that of plants grown in fritted clay.

Bidirectional Selection for Nitrogenase Activity and Shoot Dry Weight Among Late Generation Progenies of a Virginia x Spanish Peanut Cross1

1986 ◽  
Vol 13 (2) ◽  
pp. 86-89 ◽  
Author(s):  
S. Arrendell ◽  
J. C. Wynne ◽  
G. H. Elkan ◽  
T. J. Schneeweis
Keyword(s):  
Nitrogen Fixation ◽  
Plant Growth ◽  
Growth Habit ◽  
Nitrogenase Activity ◽  
Dry Weight ◽  
Fruit Weight ◽  
Shoot Dry Weight ◽  
Plant Growth Habit ◽  
The Mean ◽  
Selection For

Abstract Improvement of the host contribution to nitrogen fixation has been proposed as a method of increasing nitrogen fixation. Significant variability and generally high broad-sense heritability estimates (.60 ± .27 to .82 ± .26 for nitrogenase activity and .53 ± .29 to .85 ± .26 for shoot dry weight) have been reported for F2-derived families from a cross between the Virginia (Arachis hypogaea L. ssp. hypogaea var. hypogaea) cultivar NC 6 and the Spanish (ssp. fastigiata Waldron vulgaris Harz.) breeding line 922, indicating selection for increased nigtogen fixation should be effective in this population. Lines from this population were chosen randomly from F2-derived families selected for high and low nitrogenase activity and high and low shoot dry weight after evaluation at three dates and two locations in each of 2 years (F5 and F6 generations). This study's objectives were to evaluate the N2-fixing ability of the selected lines and to evaluate the association between plant growth habit and N2 fixation. Twenty-four lines in each of the four selection groups and the parents, NC 6 and 922, were evaluated at two sampling dates and two locations. Mean nitrogenase activity of lines selected for increased nitrogenase activity was significantly greater than the mean of the lines selected for low nitrogenase activity. Improved nitrogenase activity was associated with increased fruit weight. The fruit weight mean of the group selected for increased fruit weight. The fruit weight mean of the group selected for increased nitrogenase activity was 39% greater than the mean of the group selected for low nitrogenase activity. Mean shoot dry weight of lines selected for increased shoot dry weight was significantly greater than the mean of the lines selected for low shoot dry weight; however, the fruit weight means of these two groups did not differ. It was hypothesized that selection for increased N2 fixation in a population derived from a cross between Virginia and Spanish types would eliminate genotypes with Spanish growth habit. Groups selected for high nitrogenase activity and for high shoot dry weight had longer and wider leaflets, longer cotyledonary laterals and greater main stem height than did their respective low selection groups. However, these traits chosen to characterize plant growth habit were inadequate in discriminating parental growth habits. Consequently, the data neither substantiated nor refuted the hypothesis.

scholarly journals Elucidating the Potential of Native Rhizobial Isolates to Improve Biological Nitrogen Fixation and Growth of Common Bean and Soybean in Smallholder Farming Systems of Kenya

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Ernest Wandera Ouma ◽  
Anne Mercy Asango ◽  
John Maingi ◽  
Ezekiel Mugendi Njeru
Keyword(s):  
Nitrogen Fixation ◽  
Common Bean ◽  
Farming Systems ◽  
Dry Weight ◽  
Field Studies ◽  
Smallholder Farming ◽  
Shoot Dry Weight ◽  
Smallholder Farming Systems ◽  
Commercial Inoculant ◽  
Biological Nitrogen

Identification of effective indigenous rhizobia isolates would lead to development of efficient and affordable rhizobia inoculants. These can promote nitrogen fixation in smallholder farming systems of Kenya. To realize this purpose, two experiments were conducted under greenhouse conditions using two common bean cultivars; Mwezi moja (bush type) and Mwitemania (climbing type) along with soybean cultivar SB 8. In the first experiment, the common bean cultivars were treated with rhizobia inoculants including a consortium of native isolates, commercial isolate (CIAT 899), a mixture of native isolates and CIAT 899, and a control with no inoculation. After 30 days, the crop was assessed for nodulation, shoot and root dry weights, and morphological features. In the second experiment, soybean was inoculated with a consortium of native isolates, commercial inoculant (USDA 110), and a mixture of commercial and native isolates. Remarkably, the native isolates significantly (p<0.001) increased nodulation and shoot dry weight across the two common bean varieties compared to the commercial inoculant, CIAT 899. Mixing of the native rhizobia species and commercial inoculant did not show any further increase in nodulation and shoot performance in both crops. Further field studies will ascertain the effectiveness and efficiency of the tested indigenous isolates.

A comparison of the effect of straw incorporation and CO2 enrichment on the growth, nitrogen fixation and yield of soya beans

1976 ◽  
Vol 87 (1) ◽  
pp. 181-185 ◽  
Author(s):  
K. Shivashankar ◽  
K. Vlassak ◽  
J. Livens
Keyword(s):  
Nitrogen Fixation ◽  
Grain Yield ◽  
Root Nodules ◽  
Co2 Enrichment ◽  
Dry Weight ◽  
Growth And Yield ◽  
Culture Experiment ◽  
Fixation Capacity ◽  
The Mean ◽  
Straw Incorporation

SUMMARYIn a glasshouse pot culture experiment, the effect of adding straw at 3 and 6 t/ha with and without CO2 enrichment treatments at 1000 mg/1 from flowering to the pod-filling stage in open top chambers was evaluated on the growth and yield of soya beans in relation to nitrogen fixation. N2-ase activity of the soya-bean root nodules as determined by the acetylene reduction technique indicated that (1) straw on average gave significantly 34 and 43% higher N2-ase activity at 3 and 6 t/ha respectively than the controls; (2) CO2 treatments on average increased the activity by 34% compared with the no CO2 treatments; and (3) the mean N2-ase activity nearly doubled from 9·7 μg/h/plant in the control to 18·7 and 19·7 μg/h/plant with straw incorporation in conjunction with CO2 enrichment. High correlations were observed between weight of nodules and dry weight of leaves, between dry weight of nodules and grain yield and between dry weight of leaves and grain yield. Incorporation of straw was found to be beneficial in increasing CO2 content of soil air and in improving the growth and development of the plants. This study lends support to a hypothesis that straw can be considered to provide a partial substitute for the expensive CO2 enrichment treatment for improving N2(C2H2) fixation capacity and thereby the general growth and yield of crops.

scholarly journals Differential Regulation of Two Divergent Sinorhizobium meliloti Genes for HPII-Like Catalases during Free-Living Growth and Protective Role of Both Catalases during Symbiosis

1999 ◽  
Vol 181 (8) ◽  
pp. 2634-2639 ◽  
Author(s):  
Samuel Sigaud ◽  
Vanessa Becquet ◽  
Pierre Frendo ◽  
Alain Puppo ◽  
Didier Hérouart
Keyword(s):  
Nitrogen Fixation ◽  
Sinorhizobium Meliloti ◽  
Protective Role ◽  
Transcription Level ◽  
Dramatic Decrease ◽  
Free Living ◽  
Gene Encoding ◽  
Fixation Capacity ◽  
Minimum Medium

ABSTRACT Two catalases, KatA and KatB, have been detected inSinorhizobium meliloti growing on rich medium. Here we characterize a new catalase gene encoding a third catalase (KatC). KatC activity was detectable only at the end of the stationary phase inS. meliloti growing in minimum medium, whereas KatA activity was found during the exponential phase. Analysis with akatC-lacZ fusion demonstrated that katCexpression is mainly regulated at the transcription level. An increase of catalase activity correlating with KatA induction was detected in bacteroids. A dramatic decrease of nitrogen fixation capacity in a katA katC double mutant was observed, suggesting that these catalases are very important for the protection of the nitrogen fixation process.

Liming and choice of pasture species improve rhizobial persistence in an acidic chromosol (red-brown earth)

2005 ◽  
Vol 45 (3) ◽  
pp. 247 ◽  
Author(s):  
E. A. Roesner ◽  
N. A. Fettell ◽  
J. Brockwell
Keyword(s):  
Nitrogen Fixation ◽  
Soil Ph ◽  
Dry Matter ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Root Nodule ◽  
Nodule Bacterium ◽  
Nitrogen Response ◽  
Barrel Medic ◽  
Medicago Species

An experiment was conducted to determine the persistence of soil root-nodule bacteria as influenced by different rates of lime and the previous pasture species. The work was done at Condobolin, central-western New South Wales, on a chromosol (red-brown earth), acidic in the upper profile (pHCa 4.6), which was representative of soils for an extensive region of the eastern Australian wheat belt. In autumn 1997, the experimental area was treated with 4 rates (6.0 t/ha, 3.0 t/ha, 1.5 t/ha, nil) of finely-ground agricultural limestone and sown with 5 pasture species: lucerne (Medicago sativa), barrel medic (M. truncatula), subterranean clover (Trifolium subterraneum), rose clover (T. hirtum) and ryegrass (Lolium rigidum). The pastures were removed with herbicide and cultivation in September 2000. The land lay fallow for 9 months and then was sown to wheat (Triticum aestivum) in autumn 2001 and again in autumn 2002. The most probable numbers of soil (0–10 cm) populations of the root–nodule bacterium for Medicago species (Sinorhizobium meliloti) and for the Trifolium species (Rhizobium leguminosarum bv. trifolii) were counted in May 2001 and May 2002. Soil pH, which was significantly (P<0.05) elevated 12 months after liming, declined substantially during the next 4 years although there was no concomitant decline in the pH of unlimed soil. The pasture species were highly productive of both pasture dry matter and nitrogen. The majority of legume pasture nitrogen was a consequence of symbiotic nitrogen fixation. There was a small but significant (P<0.05) dry matter response to application of lime in lucerne and barrel medic, and a larger nitrogen response to liming in lucerne, barrel medic and rose clover. Nitrogen fixation by rose clover appeared suboptimal. It was assumed from the density of plants that large populations of rhizobia developed in the soil during the growth of the legumes. Nine months after removal of the pasture, rhizobia numbers had fallen to low levels but did not fall further during the following year. The initial fall was attributed to high soil temperatures and low soil moisture during the Condobolin summer. The population of rhizobia for Trifolium species was about twice that of the rhizobia for Medicago species but the difference was not statistically significant. Liming had an overriding influence on the size of rhizobial populations, except in plots that had previously grown ryegrass where numbers remained low irrespective of rate of liming. Overall, most probable numbers escalated with each increase in rate of liming, from 10/g soil in the nil lime plots to 708/g in the 6 t/ha lime plots. The rhizobial homology of the pasture species (i.e. Sinorhizobium meliloti for the Medicago species and Rhizobium leguminosarum bv. trifolii for the Trifolium species) had an underlying but major influence on most probable numbers and in determining which rhizobial species occurred more commonly. Estimated populations of rhizobia in soils from homologous legumes were about 8 times those found in soils from non-homologous legumes. The benefits of applying lime to this red-brown earth soil may not have been merely a consequence of correction of low soil pH; increased levels of calcium may also have had a role. The results are discussed in relation to re-establishment of legume leys after the cereal phase of the cropping system.

scholarly journals Changes in N2 fixation in Stylosanthes scabra derived from tissue culture

1997 ◽  
Vol 20 (4) ◽  
pp. 713-716 ◽  
Author(s):  
Maria José Valarini ◽  
Ivani Pozar Otsuk ◽  
Maria Lucia Carneiro Vieira
Keyword(s):  
Tissue Culture ◽  
Nitrogen Fixation ◽  
N2 Fixation ◽  
Acid Soils ◽  
Dry Weight ◽  
Acetylene Reduction Activity ◽  
Shoot Dry Weight ◽  
Reduction Activity ◽  
Randomized Design ◽  
Stylosanthes Scabra

Plants were regenerated from leaf-derived callus culture of Stylosanthes scabra, a polyploid legume tolerant to drought and adapted to acid soils. A total of 168 regenerants were planted out in Leonard jars in a complete randomized design. Nitrogen fixation and vegetative growth were indirectly evaluated by shoot dry weight, root dry weight, shoot N content and acetylene reduction activity. The results showed higher variation in the regenerants than in controls not submitted to tissue culture. Significant differences were found for all nitrogen fixation related-traits

Sign in / Sign up

Export Citation Format

Share Document