162,530 research outputs found
Regulation of Azorhizobium caulinodans ORS571 nitrogen fixation (NIF/FIX) genes
No full textBiological nitrogen fixation is the microbial process by which atmospheric dinitrogen (N 2 ) is reduced to ammonia. In all microbes studied, dinitrogen reduction is catalyzed by a highly conserved enzyme complex, called nitrogenase. The nitrogenase subunits and functions required for nitrogenase assembly and activity are encoded by the nitrogen fixation (nif/fix) genes.Nitrogen-fixing organisms can be roughly divided into two major groups: the free-living nitrogen fixing (diazotrophic) species, such as Klebsiella pneumoniae, Azotobacter vinelandii and Rhodobacter capsulatus, and symbiotically N 2 fixing organisms, such as Rhizobium species and Bradyrhizobium japonicum.The fate of the ammonia produced by these two distinct groups of nitrogen fixing organisms is quite different. While free-living nitrogen-fixing organisms will assimilate the ammonia produced for their own growth (diazotrophy), the strictly symbiotically nitrogen-fixing organisms (predominantly) excrete the ammonia into the cytoplasm of infected plant cells, to be assimilated by the host. The regulation of nitrogen fixation (nif/fix) gene expression is quite different as well, and has been difficult to compare directly between diazotrophs and strictly symbiotic nitrogen fixing organisms. The discovery of Azorhizobium caulinodans ORS571, a tropical rhizobium capable of both diazotrophy and symbiotic nitrogen fixation in stem- and root nodules induced on its host, the tropical shrub Sesbania rostrata, changed this situation and has allowed a direct comparison of (nif/fix) gene regulation in the diazotrophic versus symbiotic state. This unusual organism was chosen for the research reported in this thesis, which focuses on the expression of the central (nif/fix) regulatory gene nifA , a gene which is essential for diazotrophic growth and symbiotic nitrogen fixation, and which responds to a complex regulatory circuit.In chapter 2 a current review of the regulation of nitrogen fixation genes is presented. The review focuses on the regulation of nifA gene expression and NifA activity in different bacterial species.In chapter 3 the involvement of ntr-mediated control of the nifA promoter via the -24/-12 element is analyzed by site-specific mutagenesis and chimeric nifA - lacZ reporter gene fusions integrated into the A. caulinodans chromosome. The -24/-12 promoter element was shown to be important for nifA gene expression suggesting the involvement of a σ54 (NtrA; RpoN)-type transcription factor in nifA gene regulation.Chapter 4 addresses the involvement of a ntrA(rpoN) -like sigma factor in nifA expression, and reports the cloning and analysis of an A. caulinodans ntrA(rpoN) gene. Although the ntrA(rpoN) gene identified in this study was shown to control the expression of some of the A.caulinodans nif genes (like nifHDK) and nitrate assimilation genes, it did not appear to regulate the expression of nifA , suggesting the presence of an additional ( nifA specific) ntrA ( rpoN )-equivalent gene.To search for trans -acting factors involved in the regulation of the nifA expression, the in vitro interaction of proteins in A. caulinodans crude cell extracts with the nifA regulatory region was studied by gel retardation assays. Chapter 5 presents the binding of (a) sequence-specific protein(s) in extracts of A.caulinodans to the nifA 5' upstream region. However the nature of the protein(s) and the exact location of the binding site in the nifA 5' upstream region remains to be determined.During the preparation of crude cell extracts from A. caulinodans fi xLJ and fixK mutant strains, large amounts of a red/pink, UV fluorescent pigment was observed in the culture medium. Chapter 6 describes the isolation and characterization of this pigment.Chapter 7 describes the isolation and characterization of an leuA -like gene of A.caulinodans which was incidentally identified with an Escherichia coli fnr probe. Comparison of the 5' upstream region of the A. caulinodans leuA gene with the leu operons of other organisms suggest a conserved regulation mechanism for the expression (transcription attenuation), found in many amino acid biosynthetic operons.Finally in chapter 8 the current model for nitrogen fixation gene regulation in A.caulinodans, deduced from the studies presented in this thesis and previous data, is presented
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Groundwater and climate change: threats and opportunities
No full textThe important role of groundwater in adaptation to climate change is explored, and the competing threats and opportunities that climate change pose to groundwater systems are evaluated. This has been achieved through a review of current thinking on the complex interactions between human activities, climate and the hydrological cycle affecting groundwater quantity and quality, across different regions and time scales
Electrophoresis of fd-virus particles: Experiments and an analysis of the effect of finite rod lengths
No full textThe electrophoretic mobility of rodlike fd viruses is measured and compared to theory, with the theoretical calculations performed according to Stigter (Stigter, D. Charged Colloidal Cylinder with a Gouy Double-Layer. J. Colloid Interface Sci. 1975, 53, 296-306. Stigter, D. Electrophoresis of Highly Charged Colloidal Cylinders in Univalent Salt- Solutions. 1. Mobility in Transverse Field. J. Phys. Chem. 1978, 82, 1417-1423. Stigter, D. Electrophoresis of Highly Charged Colloidal Cylinders in Univalent Salt Solutions. 2. Random Orientation in External Field and Application to Polyelectrolytes. J. Phys. Chem. 1978, 82, 1424-1429. Stigter, D. Theory of Conductance of Colloidal Electrolytes in Univalent Salt Solutions. J. Phys. Chem. 1979, 83, 1663-1670), who describes the electrophoretic mobility of infinite cylinders including relaxation effects. Using the dissociation constants of the ionizable groups on the surfaces of the fd viruses, we can calculate the mobility without any adjustable parameter (apart from the possible Stern layer thickness). In addition, the approximation in the theoretical description of Stigter (and others) of using a model of infinitely long cylinders, which consequently is independent of the aspect ratio, is examined by performing more elaborate numerical calculations for finite cylinders. It is shown that, although the electrophoretic mobility of cylindrical particles in the limit of low ionic strength depends on the aspect ratio much more than "end effects", at moderate and high ionic strengths the finite and infinite cylinder models differ only to a degree that can be attributed to end effects. Furthermore, the range of validity of the Stokes regime is systematically calculated
Murder on the mountain: author talk with Peter J. Wosh
No full textAuthor talk by Peter J. Wosh on May 5th, 2022, on his book, "Murder on the Mountain: crime, passion, and punishment in gilded age New Jersey.
Mr. Melvin J. Collier, RWWL AUC, June 2011
No full textThis video is a conversation with Mr. Melvin J. Collier. Mr. Collier talks about his book, "From Mississippi to Africa: A Journey of Discovery". Daniel Le, AUC Woodruff Library, is the interviewer
A Tripartite Post-Recession Rebalancing
No full textIn this latest Advance & Rutgers Report, entitled “A Tripartite Post-Recession Rebalancing,” Dean James W. Hughes and Professor Joseph J. Seneca deliver an incisive assessment of the current market conditions and obstacles in the path of our economic recovery. They offer a statistical cautionary tale that the private and public sector need to hear and acknowledge in order for the economy to make continued progress.This report was published as Issue Paper Number 7, November 2011, in Advance & Rutgers Report
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
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