577 research outputs found
Electron transport phosphorylation in rumen butyrivibrios: unprecedented ATP yield for glucose fermentation to butyrate.
From a genomic analysis of rumen butyrivibrios (Butyrivibrio and Pseudobutyrivibrio sp.), we have re-evaluated the contribution of electron transport phosphorylation (ETP) to ATP formation in this group. This group is unique in that most (76%) genomes were predicted to possess genes for both Ech and Rnf transmembrane ion pumps. These pumps act in concert with the NifJ and Bcd-Etf to form a electrochemical potential (ΔμH(+) and ΔμNa(+)), which drives ATP synthesis by ETP. Of the 62 total butyrivibrio genomes currently available from the Hungate 1000 project, all 62 were predicted to possess NifJ, which reduces oxidized ferredoxin (Fdox) during pyruvate conversion to acetyl-CoA. All 62 possessed all subunits of Bcd-Etf, which reduces Fdox and oxidizes reduced NAD during crotonyl-CoA reduction. Additionally, 61 genomes possessed all subunits of the Rnf, which generates ΔμH(+) or ΔμNa(+) from oxidation of reduced Fd (Fdred) and reduction of oxidized NAD. Further, 47 genomes possessed all six subunits of the Ech, which generates ΔμH(+) from oxidation of Fdred. For glucose fermentation to butyrate and H2, the electrochemical potential established should drive synthesis of ∼1.5 ATP by the F0F1-ATP synthase (possessed by all 62 genomes). The total yield is ∼4.5 ATP/glucose after accounting for three ATP formed by classic substrate-level phosphorylation, and it is one the highest yields for any glucose fermentation. The yield was the same when unsaturated fatty acid bonds, not H(+), served as the electron acceptor (as during biohydrogenation). Possession of both Ech and Rnf had been previously documented in only a few sulfate-reducers, was rare in other rumen prokaryotic genomes in our analysis, and may confer an energetic advantage to rumen butyrivibrios. This unique energy conservation system might enhance the butyrivibrios' ability to overcome growth inhibition by unsaturated fatty acids, as postulated herein
Inversion of hyperelliptic integrals of arbitrary genus with application to particle motion in General Relativity
The description of many dynamical problems like the particle motion in higher
dimensional spherically and axially symmetric space-times is reduced to the
inversion of a holomorphic hyperelliptic integral. The result of the inversion
is defined only locally, and is done using the algebro-geometric techniques of
the standard Jacobi inversion problem and the foregoing restriction to the
--divisor. For a representation of the hyperelliptic functions the
Klein--Weierstra{\ss} multivariable sigma function is introduced. It is shown
that all parameters needed for the calculations like period matrices and
Abelian images of branch points can be expressed in terms of the periods of
holomorphic differentials and theta-constants. The cases of genus two and three
are considered in detail. The method is exemplified by particle motion
associated with a genus three hyperelliptic curve
Geodesic equations and algebro-geometric methods
For an investigation of the physical properties of gravitational fields the
observation of massive test particles and light is very useful. The
characteristic features of a given space-time may be decoded by studying the
complete set of all possible geodesic motions. Such a thorough analysis can be
accomplished most effectively by using analytical methods to solve the geodesic
equation. In this contribution, the use of elliptic functions and their
generalizations for solving the geodesic equation in a wide range of well known
space-times, which are part of the general Pleba\'nski-Demia\'nski family of
solutions, will be presented. In addition, the definition and calculation of
observable effects like the perihelion shift will be presented and further
applications of the presented methods will be outlined.Comment: 8 pages, no figures; based on presentation at the conference
"Relativity and Gravitation: 100 Years after Einstein in Prague," Prague,
2012. Relativity and Gravitation, volume 157 of Springer Proceedings in
Physics, p 91. Springer International Publishing, 201
Analytic solutions of the geodesic equation in axially symmetric space-times
The complete sets of analytic solutions of the geodesic equation in
Taub--NUT--(anti-)de Sitter, Kerr--(anti-)de Sitter and also in general
Plebanski--Demianski space--times without acceleration are presented. The
solutions are given in terms of the Kleinian sigma functions.Comment: 4 pages, 4 figures, accepted for publication in EP
Life inside black holes
We consider test planet and photon orbits of the third kind inside a black
hole, which are stable, periodic and neither come out of the black hole nor
terminate at the singularity. Interiors of supermassive black holes may be
inhabited by advanced civilizations living on planets with the third-kind
orbits. In principle, one can get information from the interiors of black holes
by observing their white hole counterparts.Comment: 4 pages, 2 figure
Particle motion in the field of a five-dimensional charged black hole
In this paper, we have investigated the geodesics of neutral particles near a
five-dimensional charged black hole using a comparative approach. The effective
potential method is used to determine the location of the horizons and to study
radial and circular trajectories. This also helps us to analyze the stability
of radial and circular orbits. The radius of the innermost stable circular
orbits have also been determined. Contrary to the case of massive particles for
which, the circular orbits may have up to eight possible values of specific
radius, we find that the photons will only have two distinct values for the
specific radii of circular trajectories. Finally we have used the dynamical
systems analysis to determine the critical points and the nature of the
trajectories for the timelike and null geodesics.Comment: 15 pages, accepted for publication in Astrophysics and Space Scienc
Ruminal bacteria and protozoa composition, digestibility, and amino acid profile determined by multiple hydrolysis times
Rumen digestion kinetics, microbial yield, and omasal flows of nonmicrobial, bacterial, and protozoal amino acids in lactating dairy cattle fed fermentation by-products or urea as a soluble nitrogen source
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