STUDIES ON THE LEGUME ROOT NODULE BACTERIA: II. THE PRODUCTION AND BEHAVIOR OF COLONIAL MUTANTS PRODUCED BY X-RAY IRRADIATION

1952 ◽  
Vol 30 (2) ◽  
pp. 125-130 ◽  
Author(s):  
D. C. Jordan
Keyword(s):  
Root Nodule ◽  
Effective Strain ◽  
Sterile Plant ◽  
Nodule Bacteria ◽  
Artificial Medium ◽  
Serial Transfer ◽  
Root Nodule Bacteria ◽  
X Ray ◽  
Colonial Morphology ◽  
And Behavior

Four distinct types of colonial mutation were obtained by X-ray irradiation of a parasitic strain of alfalfa Rhizobium. Two types were procured from an effective strain. Colonial morphology remained stable throughout serial transfer on artificial medium, but changed considerably after one plant passage. Three variants derived from the parasitic parent were found to be efficient in nitrogen fixation when tested by sterile plant growth procedures and the Virtanen technique. This efficiency increased during the course of two plant passages. Colonial variation and effectivity changes occurred independently of one another.

Functional Specificity of the nifA Gene Product within the Group of Root Nodule Bacteria

Microbiology ◽  
2021 ◽  
Vol 90 (4) ◽  
pp. 481-488
Author(s):  
A. A. Vladimirova ◽  
R. S. Gumenko ◽  
E. S. Akimova ◽  
Al. Kh. Baymiev ◽  
An. Kh. Baymiev
Keyword(s):  
Gene Product ◽  
Root Nodule ◽  
Nodule Bacteria ◽  
Functional Specificity ◽  
Root Nodule Bacteria ◽  
Nifa Gene

scholarly journals Quantitative evaluation of acidity tolerance of root nodule bacteria

1999 ◽  
Vol 30 (3) ◽  
pp. 203-208 ◽  
Author(s):  
Luiz Antonio de Oliveira ◽  
Hélio Paracaima de Magalhães
Keyword(s):  
Root Nodule ◽  
Maximum Growth ◽  
Nodule Bacteria ◽  
Root Nodule Bacteria ◽  
Soil Persistence ◽  
Statistical Precision ◽  
Visible Growth ◽  
Selection For ◽  
Growth Scores ◽  
Selection Of

Quantification of acidity tolerance in the laboratory may be the first step in rhizobial strain selection for the Amazon region. The present method evaluated rhizobia in Petri dishes with YMA medium at pH 6.5 (control) and 4.5, using scores of 1.0 (sensitive, "no visible" growth) to 4.0 (tolerant, maximum growth). Growth evaluations were done at 6, 9, 12, 15 and 18 day periods. This method permits preliminary selection of root nodule bacteria from Amazonian soils with statistical precision. Among the 31 rhizobia strains initially tested, the INPA strains 048, 078, and 671 presented scores of 4.0 at both pHs after 9 days of growth. Strain analyses using a less rigorous criterion (growth scores higher than 3.0) included in this highly tolerant group the INPA strains 511, 565, 576, 632, 649, and 658, which grew on the most diluted zone (zone 4) after 9 days. Tolerant strains still must be tested for nitrogen fixation effectiveness, competitiveness for nodule sites, and soil persistence before their recommendation as inoculants.

Application of molecular techniques to studies in Rhizobium ecology: a review

2001 ◽  
Vol 41 (3) ◽  
pp. 299 ◽  
Author(s):  
J. E. Thies ◽  
E. M. Holmes ◽  
A. Vachot
Keyword(s):  
Root Nodule ◽  
Molecular Techniques ◽  
Nodule Bacteria ◽  
Bacterial Genomes ◽  
Root Nodule Bacteria ◽  
Bacterial Signaling ◽  
Field Environment ◽  
Background Population ◽  
Insight Into ◽  
Made In

The symbiosis between legumes and their specific root-nodule bacteria, rhizobia, has been employed to improve agricultural productivity for most of the 20th century. During this time, great advances have been made in our knowledge of both plant and bacterial genomes, the biochemistry of the symbiosis, plant and bacterial signaling and the measurement of nitrogen fixation. However, knowledge of the ecology of the bacterial symbiont has lagged behind, largely due to a lack of practical techniques that can be used to monitor and assess the performance of these bacteria in the field. Most techniques developed in the last few decades have relied on somehow ‘marking’ individual strains to allow us to follow their fate in the field environment. Such techniques, while providing knowledge of the success or failure of specific strains in a range of environments, have not allowed insight into the nature of the pre-existing rhizobial populations in these sites, nor the interaction between marked strains and the background population. The advent of molecular techniques has revolutionised the study of Rhizobium ecology by allowing us to follow the flux of a variety of ecotypes within a particular site and to examine how introduced rhizobia interact with a genetically diverse background. In addition, molecular techniques have increased our understanding of how individual strains and populations of root-nodule bacteria respond to changes in the environment and how genetic diversity evolves in field sites over time. This review focuses on recently developed molecular techniques that hold promise for continuing to develop our understanding of Rhizobium ecology and how these can be used to address a range of applied problems to yield new insights into rhizobial life in soil and as legume symbionts.

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