An effective strain of Frankia from Casuarina sp.

1983 ◽  
Vol 61 (11) ◽  
pp. 2815-2821 ◽  
Author(s):  
H. G. Diem ◽  
D. Gauthier ◽  
Y. Dommergues
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Pure Culture ◽  
Root Nodules ◽  
Effective Strain ◽  
Root Hairs ◽  
Culture Conditions ◽  
Reduction Technique ◽  
Standard Culture

A strain of Frankia, designated Cj1-82, from root nodules of a hybrid of Casuarina junghuhniana and C. equisetifolia has been isolated in pure culture. When grown under standard culture conditions, Cj1-82 exhibited the following characteristics: cushionlike colonies with short, wide hyphae and, in addition to typical sporangia, intercalary elongated sporangialike structures (SLS) which could be disrupted into sporelike units. No vesicles were found. When inoculated into the rhizosphere of C. equisetifolia, Cj1-82 produced vesicles. Reinfection of seedlings of C. equisetifolia was achieved repeatedly with inocula prepared from a suspension of Cj1-82. Sequences of infection of root hairs were described. Fourteen days after inoculation, nodules were apparent on the roots. Nodules were shown to be effective in nitrogen fixation as assessed by the acetylene-reduction technique.

Ineffectiveness of viomycin-resistant mutants of Rhizobium meliloti

1969 ◽  
Vol 15 (7) ◽  
pp. 671-675 ◽  
Author(s):  
G. S. Hendry ◽  
D. C. Jordan
Keyword(s):  
Cell Wall ◽  
Nitrogen Fixation ◽  
Parent Strain ◽  
Rhizobium Meliloti ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Effective Strain ◽  
One Step ◽  
Increased Sensitivity ◽  
Resistant Mutants

Under clearly defined conditions one-step acquisition of viomycin resistance by a normally effective strain of Rhizobium meliloti resulted in one-step acquisition of ineffectiveness in nitrogen fixation, which probably occurred with a one-gene change in the R. meliloti genome. Two-step mutants retained their ability to produce root nodules but such nodules also were ineffective. Increased sensitivity of the viomycin-resistant mutants to glycine and D-alanine was not noted. Bacteroids were not seen in nodules formed by the viomycin-resistant mutants on their homologous host plant. Nitrogenase activity was not detected, by acetylene reduction, in detached ineffective nodules, whereas effective nodules formed 10.6 μmoles of ethylene per hour per gram of nodules. Growth of the effective parent strain in a low concentration of viomycin resulted in elongation and swelling of the cells so that they appeared as artificially produced bacteroids. Viomycin-resistant mutants did not undergo this transformation. Antigens could be readily extracted by hot- and cold-saline extraction of wet packed cells of both resistant and sensitive cultures but antigenic differences, which may have indicated cell wall differences, were not noted.

scholarly journals Transcription Profiling of Soybean Nodulation by Bradyrhizobium japonicum

2008 ◽  
Vol 21 (5) ◽  
pp. 631-645 ◽  
Author(s):  
Laurent Brechenmacher ◽  
Moon-Young Kim ◽  
Marisol Benitez ◽  
Min Li ◽  
Trupti Joshi ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Bradyrhizobium Japonicum ◽  
Root Nodules ◽  
Expression Patterns ◽  
Root Hairs ◽  
Defense Responses ◽  
Nodule Development ◽  
Plant Defense Responses ◽  
Polymerase Chain ◽  
High Level

Legumes interact with nodulating bacteria that convert atmospheric nitrogen into ammonia for plant use. This nitrogen fixation takes place within root nodules that form after infection of root hairs by compatible rhizobia. Using cDNA microarrays, we monitored gene expression in soybean (Glycine max) inoculated with the nodulating bacterium Bradyrhizobium japonicum 4, 8, and 16 days after inoculation, timepoints that coincide with nodule development and the onset of nitrogen fixation. This experiment identified several thousand genes that were differentially expressed in response to B. japonicum inoculation. Expression of 27 genes was analyzed by quantitative reverse transcriptase-polymerase chain reaction, and their expression patterns mimicked the microarray results, confirming integrity of analyses. The microarray results suggest that B. japonicum reduces plant defense responses during nodule development. In addition, the data revealed a high level of regulatory complexity (transcriptional, post-transcriptional, translational, post-translational) that is likely essential for development of the symbiosis and adjustment to an altered nutritional status.

Confirmation of the infectivity of a free-living actinomycete isolated from Comptonia peregrina root nodules by immunological and ultrastructural studies

1978 ◽  
Vol 56 (21) ◽  
pp. 2621-2635 ◽  
Author(s):  
Maurice Lalonde
Keyword(s):  
Nitrogen Fixation ◽  
Pure Culture ◽  
Root Nodules ◽  
Free Living ◽  
Ultrastructural Studies ◽  
Nitrogen Fixation Activity ◽  
Fixation Activity ◽  
Membrane Envelope ◽  
Freeze Etching

The inoculation of the host plant Comptonia peregrina (L.) Coult. (Myrica asplenifolia L.) by a pure culture of a free-living actinomycete, isolated from Comptonia root nodules by Callaham et al. (1978, Science, 199: 899–902), was successful. Short-term and long-term nodulation tests confirmed the infectivity of the Comptonia isolate. Acetylene reduction assays of the nodules induced by this prokaryote isolate demonstrated nitrogen fixation activity. This nitrogen fixation activity was able to sustain a prolific growth of the nodulated host plants growing in a N-free substrate. Indirect immufluorescence reactions, using specific gamma globulin against the actinomycetal isolate of the Comptonia root nodule, demonstrated the identity of this actinomycete in these in vitro produced Comptonia root nodules. Ultrastructure of the Comptonia isolate, developing as a free-living or endophytic actinomycete, was observed by light microscopy, freeze etching, and transmission electron microscopy. The free-living filamentous and sporulating isolate produced typical hyphae and vesicles when growing as an endophyte in the Comptonia nodule. These endophytic hyphae and vesicles were always encapsulated by a polysaccharide material which was surrounded by a host membrane envelope. A polysaccharide capsule was not demonstrated on the free-living Comptonia isolate. The endophytic vesicles were club shaped and highly septate. Such vesicles were never produced by the free-living isolate growing in an artificial medium. The Comptonia isolate is a spore former in pure culture and was able to sporulate in basal tissues of 5-month-old Comptonia nodules.

Nitrogen Fixation by Native Australian Legumes

1981 ◽  
Vol 29 (2) ◽  
pp. 143 ◽  
Author(s):  
AC Lawrie
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Sand Dune ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Sand Dunes ◽  
Late Summer ◽  
Open Forest ◽  
Seasonal And Diurnal Variations ◽  
Major Factors

Nitrogen fixation was studied by the acetylene-reduction technique in root nodules of 10 native Australian legumes in three habitats in Victoria: low open-forest. sandy heathland and coastal sand dunes. Nodular activity reached a maximum in spring (and in autumn in sand-dune species), declined to a minimum in late summer and continued at a low level throughout winter. Mean nitrogenase activity was 1.73 μmol C2H2 reduced g-1 fresh wt nodules h-1, with spring maxima 8-250 times summer minima. It is suggested that variations in rainfall and temperature were the major factors influencing seasonal variations in nodular activity. Estiniates of minimum acetylene reduction per hectare per year were derived from measurements of seasonal and diurnal variations in acetylene reduction and abundance of nodules per hectare, and were used to derive approximate minimum values for nitrogen fixation of 0.004-0.746 kg ha-1 yr-1. The quantities of nitrogen fixed are compared with other reports and the significance of nitrogen fixation by these native legumes is discussed.

In Situ Studies on Nitrogen Fixation with the Acetylene Reduction Technique

Science ◽  
1967 ◽  
Vol 158 (3800) ◽  
pp. 536-536 ◽  
Author(s):  
W. D. P. Stewart ◽  
G. P. Fitzgerald ◽  
R. H. Burris
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Reduction Technique ◽  
In Situ Studies

Effect of phosphate supply and competition from grasses on growth and nitrogen fixation of Medicago trunculata

1981 ◽  
Vol 32 (5) ◽  
pp. 761 ◽  
Author(s):  
ABK Dahmane ◽  
RD Graham
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogen Content ◽  
Acetylene Reduction ◽  
Pure Culture ◽  
Dry Matter ◽  
Considerable Variability ◽  
Fixed Nitrogen ◽  
Intact Plants ◽  
Medicago Trunculata ◽  
Phosphate Supply

Medic plants and ryegrass were grown in small pots in a glasshouse in monoculture (six plants per pot) or in mixture (three plants of each species) at eight rates of phosphate application. After 10 weeks, the rate of nitrogen fixation was estimated by the acetylene reduction (AR) technique on the intact plants in soil, after which the plants were harvested, both shoots and roots. The yield of medic, in both monoculture and mixture, increased with increasing rate of phosphate application to an optimum at a level of 160 ppm phosphorus and then decreased again at higher phosphate levels. AR activity was similarly dependent on phosphate application and was optimal at the same phosphate level as was yield. AR activity was extremely low in the ryegrass monocultures, the yield of which was optimized at only 10 ppm phosphorus. The community x phosphate interaction on AR activity per plant of medic was not statistically significant, there being considerable variability in this measurement; the suppression of nitrogen fixation by competition from ryegrass near its own phosphate optimum was not therefore established in this study, but remains a possibility. Ryegrass plants benefited individually from growing in mixed culture with the legume, producing as much shoot dry matter from three plants in mixture as from six in monoculture. The advantage in mixture was due either to reduced competition offered by medic or to transfer of fixed nitrogen from legume to grass. Higher concentrations and contents of nitrogen per plant in mixture provided circumstantial evidence for the latter. However, on a pot basis, nitrogen content of ryegrass was similar in pure culture and in mixture. The relevance of the data to the results of a survey of farmers' fields is discussed.

scholarly journals Conditional sanctioning in a legume–Rhizobium mutualism

2021 ◽  
Vol 118 (19) ◽  
pp. e2025760118
Author(s):  
Annet Westhoek ◽  
Laura J. Clark ◽  
Michael Culbert ◽  
Neil Dalchau ◽  
Megan Griffiths ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Developmental Stages ◽  
Root Nodules ◽  
Effective Strain ◽  
Nitrogen Fixing Bacteria ◽  
Nodule Size ◽  
Carbon Supply ◽  
Model Predictions ◽  
Viable Bacteria ◽  
Lower Carbon

Legumes are high in protein and form a valuable part of human diets due to their interaction with symbiotic nitrogen-fixing bacteria known as rhizobia. Plants house rhizobia in specialized root nodules and provide the rhizobia with carbon in return for nitrogen. However, plants usually house multiple rhizobial strains that vary in their fixation ability, so the plant faces an investment dilemma. Plants are known to sanction strains that do not fix nitrogen, but nonfixers are rare in field settings, while intermediate fixers are common. Here, we modeled how plants should respond to an intermediate fixer that was otherwise isogenic and tested model predictions using pea plants. Intermediate fixers were only tolerated when a better strain was not available. In agreement with model predictions, nodules containing the intermediate-fixing strain were large and healthy when the only alternative was a nonfixer, but nodules of the intermediate-fixing strain were small and white when the plant was coinoculated with a more effective strain. The reduction in nodule size was preceded by a lower carbon supply to the nodule even before differences in nodule size could be observed. Sanctioned nodules had reduced rates of nitrogen fixation, and in later developmental stages, sanctioned nodules contained fewer viable bacteria than nonsanctioned nodules. This indicates that legumes can make conditional decisions, most likely by comparing a local nodule-dependent cue of nitrogen output with a global cue, giving them remarkable control over their symbiotic partners.

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