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  • 1
    ISSN: 1432-072X
    Keywords: Bradyrhizobium ; Electron microscopy ; Mutants ; Nitrogen fixation ; Nodulation ; Soybean ; Symbiosis ; Transposon Tn5
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The genome of the slow-growing Bradyrhizobium japonicum (strain 110) was mutagenized with transposon Tn5. A total of 1623 kanamycin/streptomycin resistant derivatives were screened in soybean infection tests for nodulation (Nod) and symbiotic nitrogen fixation (Fix). In this report we describe 14 strains possessing a stable, reproducible Nod+Fix- phenotype. These strains were also grown under microaerobic culture conditions to test them for free-living nitrogen fixation activity (Nif). In addition to strains having reduced Fix and Nif activities, there were also strains that had reduced symbiotic Fix activity but were Nif+ ex planta. Analysis of the genomic structure revealed that the majority of the strains had a single Tn5 insertion without any further apparent physical alteration. A few strains had additional insertions (by Tn5 or IS50), or a deletion, or had cointegrated part of the vector used for Tn5 mutagenesis. One of the insertions was found in a known nif gene (nifD) whereas all other mutations seem to affect different, hitherto unknown genes or operons. Several mutant strains had an altered nodulation phenotype, inducing numerous, small, widely distributed nodules. Light and electron microscopy revealed that most of these mutants were defective in different stages of bacteroid development and/or bacteroid persistence. The protein patterns of the mutants were inspected by two-dimensional gel electrophoresis after labelling microaerobic cultures with l-(35S)methionine. Of particular interest were mutants lacking a group of proteins the synthesis of which was known to be under oxygen control. Such strains can be regarded as potential regulatory mutants.
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  • 2
    ISSN: 1432-2048
    Keywords: Glutamine synthetase ; Leghaemoglobin ; Nitrogenase ; Nitrogen fixation ; Phaseolus ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The activities of glutamine synthetase (GS), nitrogenase and leghaemoglobin were measured during nodule development in Phaseolus vulgaris infected with wild-type or two non-fixing (Fix-) mutants of Rhizobium phaseoli. The large increase in GS activity which was observed during nodulation with the wild-type rhizobial strain occurred concomitantly with the detection and increase in activity of nitrogenase and the amount of leghaemoglobin. Moreover, this increase in GS was found to be due entirely to the appearance of a novel form of the enzyme (GSn1) in the nodule. The activity of the form (GSn2) similar to the root enzyme (GSr) remained constant throughout the experiment. In nodules produced by infection with the two mutant strains of Rhizobium phaseoli (JL15 and JL19) only trace amounts of GSn1 and leghaemoglobin were detected.
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  • 3
    ISSN: 1617-4623
    Keywords: Exopolysaccharide ; Legume ; Nodules ; Rhizobium ; Xanthomonas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A Tn5-induced mutant strain of R. phaseoli which failed to synthesize exopolysaccharide (EPS) was isolated and was shown to induce normal nitrogen-fixing nodules on Phaseolus beans, the host of this Rhizobium species. The corresponding wild-type Rhizobium DNA was cloned in a wide host-range vector and by isolating Tn5 insertions in this cloned DNA, mutations in a gene termed pss (polysaccharide synthesis) were isolated. These were introduced by marker exchange into near-isogenic strains of R. leguminosarum and R. phaseoli which differed only in the identity of their symbiotic plasmids. Whereas the EPS-deficient mutant strain of R. phaseoli induced normal nitrogen-fixing nodules on Phaseolus beans, the same mutation prevented nodulation of peas by a strain of R. leguminosarum which normally nodulates this host. Further, it was found that DNA cloned from the plant pathogen Xanthomonas campestris pathover campestris could correct the defect in EPS synthesis in R. leguminosarum and R. phaseoli and also restored the ability to nodulate peas to the pss::Tn5 mutant strain of R. leguminosarum.
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  • 4
    Publication Date: 2019-07-13
    Description: Turbulent base flowfields in multinozzle configurations, considering adiabatic flow and determining base pressure distribution from reverse jet impingement
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 69-570 , ; ACE(|AMERICAN INST. OF AERONAUTICS AND ASTRONAUTICS, PROPULSION JOINT SPECIALIST CONFERENCE, 5TH, U.S. AIR FORCE ACADEMY; Jun 09, 1969 - Jun 13, 1969; COLORADO SPRINGS, CO
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  • 5
    Publication Date: 2019-07-13
    Description: Plane supersonic base flows studied using integral analysis of turbulent reattachment, noting prediction of wall pressure distribution
    Keywords: AERODYNAMICS
    Type: ANNUAL AVIATION AND SPACE CONFERENCE; Jun 16, 1968 - Jun 19, 1968; BEVERLY HILLS, CA
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  • 6
    Publication Date: 2019-07-13
    Description: Plane supersonic base flows studied using integral analysis of turbulent reattachment, noting prediction of wall pressure distribution
    Keywords: AERODYNAMICS
    Type: AVIATION AND SPACE- PROGRESS AND PROSPECTS; Jun 16, 1968 - Jun 19, 1968; BEVERLY HILLS, CALIF.|; YAL SOCIETY (
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  • 7
    Publication Date: 2019-07-13
    Description: Use of surface pressures, heat-transfer rates, and flow-visualization photographs to define the flowfields for simulated infinite cylinders. Four cylindrical cross sections were studied in the experimental program, which was conducted at free-stream Mach numbers of 5 to 15, free-stream unit Reynolds numbers from 2 to 20 million per foot, and angles of attack from 30 to 90 deg. Although swept-cylinder theory provides a reasonable correlation of the measured laminar heat-transfer rates in the plane of symmetry, improved correlation with the measurements is obtained if the three-dimensional nature of the flow is taken into account. In cases where the boundary layer on the windward forebody was turbulent, the large velocity gradients near the chines produced relaminarization of the boundary layer prior to separation. The average heat-transfer-rate in the separated region, which is weakly dependent on the free-stream conditions, was found to be a linear function of the angle of attack. For a given flow condition the effect of the leeward geometry on heat transfer can be correlated by a single geometric parameter which is dependent on the location of separation.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 72-294 , American Institute of Aeronautics and Astronautics, Thermophysics Conference; Apr 10, 1972 - Apr 12, 1972; San Antonio, TX
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  • 8
    Publication Date: 2019-07-13
    Description: Turbulent base flowfields in multinozzle configurations, considering adiabatic flow and determining base pressure distribution from reverse jet impingement
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 69-570 , AMERICAN INST. OF AERONAUTICS AND ASTRONAUTICS, PROPULSION JOINT SPECIALIST CONFERENCE; Jun 09, 1969 - Jun 13, 1969; COLORADO SPRINGS, COLO.
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