There are rumen bacteria capable of degrading toxic dihydroxypyridine compounds derived from mimosine, a non-protein amino acid found in the toxic legume
Leucaena leucocephala. Activity of ...degradation of the metabolite 2,3-dihydroxypyridine (2,3-DHP) can be temporarily or permanently lost. In this study we have determined the extension of bacterial growth and degradation of 2,3-DHP under different conditions. Degradation of 2,3-DHP started once cultures reached late exponential phase, and complete degradation was achieved in 3 days. If additional 2,3-DHP was added to the cultures, complete degradation occurred within the following 12 h. Degradation of the 2,3-DHP occurred in medium (saline) containing either pyruvate, rumen fluid or arginine but not in saline supplemented with volatile fatty acids or vitamins. Strict anaerobic conditions allowed optimal culture growth and degradation of 2,3-DHP. Maintenance of cultures in medium lacking 2,3-DHP for 2 months caused loss of ability to degrade the compound. When cultured again in medium containing 2,3-DHP, cultures grew normally but only regained activity after a time lag of 4 weeks. Plasmids that could carry fundamental activities in the degradation process were not detected. The results of this work are relevant to the conditions of in vitro screening for 2,3-DHP degradation activity in rumen contents and manipulation of 2,3-DHP degrading cultures in the laboratory.
Jaramillo-Jaimes, M.T., Sifuentes-Rincón, A.M., Sánchez Torres-Esqueda, M.T., Mendoza-Martínez, G.D., Clemente-Sánchez, F., Olivera-López, J.I., Molina Hernández, M. and Martínez-Tripp, S.C. 2007. ...Genetic variability in six Mexican gray wolf (Canis lupus baileyi) populations determined by microsatellite markers. J. Appl. Anim. Res., 31: 131-136.
A study was conducted to evaluate genetic diversity in six Mexican gray wolf populations based on six microsatellite loci. Allelic frequencies, heterozygosity and genetic distances were determined with a pairwise analysis of the genetic distance means to demonstrate that the six wolf populations are genetically very close (0.17-0.41), with marked grouping between populations. Notable differences were observed between allelic frequency profiles for the six microsatellites in the six studied Mexican gray wolf populations. Further studies using Mexican gray wolf populations and other related canid populations are recommended.
We derive the relativistic chiral transport equation for massless fermions and antifermions by performing a semiclassical Foldy-Wouthuysen diagonalization of the quantum Dirac Hamiltonian. The Berry ...connection naturally emerges in the diagonalization process to modify the classical equations of motion of a fermion in an electromagnetic field. We also see that the fermion and antifermion dispersion relations are corrected at first order in the Planck constant by the Berry curvature, as previously derived by Son and Yamamoto for the particular case of vanishing temperature. Our approach does not require knowledge of the state of the system, and thus it can also be applied at high temperature. We provide support for our result by an alternative computation using an effective field theory for fermions and antifermions: the on-shell effective field theory. In this formalism, the off-shell fermionic modes are integrated out to generate an effective Lagrangian for the quasi-on-shell fermions/antifermions. The dispersion relation at leading order exactly matches the result from the semiclassical diagonalization. From the transport equation, we explicitly show how the axial and gauge anomalies are not modified at finite temperature and density despite the incorporation of the new dispersion relation into the distribution function.
We formulate the on-shell effective field theory (OSEFT) in an arbitrary frame and study its reparametrization invariance, which ensures that it respects Lorentz symmetry. In this formulation, the ...OSEFT Lagrangian looks formally equivalent to the sum over lightlike velocities of soft collinear effective field theory in the Abelian limit, but differences remain in the scale of the gauge fields involved in the two effective theories. We then use the OSEFT Lagrangian expanded in inverse powers of the on-shell energy to derive how the classical transport equations for charged massless fermions are corrected by quantum effects, as derived from quantum field theory. We provide a formulation in a full covariant way and explain how the consistent form of the chiral anomaly equation can be recovered from our results. We also show how the side-jump transformation of the distribution function associated with massless charged fermions can be derived from the reparametrization invariance transformation rules of the OSEFT quantum fields. Finally, we discuss the differences in our results with respect to others found in the literature.
Biological sequence comparison is one of the most important and basic problems in computational biology. Due to its high demands for computational power and memory, it is a very challenging task. ...Most of sequence comparison methods used are based on heuristics, which are faster but there are no guarantees that the best alignments will be produced. On the other hand, the algorithm proposed by Smith-Waterman obtains the best local alignments at the expense of very high computing power and huge memory requirements. In this article, we present and evaluate our experiments with three parallel strategies to run the Smith-Waterman algorithm in a cluster of workstations using a Distributed Shared Memory System. Our results on an eight-machine cluster presented very good speedups and indicate that impressive improvements can be achieved, depending on the strategy used. Also, we present some theoretical remarks on how to reduce the amount of memory used.
The rumen bacteriumPseudobutyrivibrio xylanivorans Mz5^sup T^ has a potent xylanolytic enzyme system. A small native peptide (asymptotically =30-kDa, designated Xyn11A) from the bacterium was first ...isolated and characterized by Edman degradation. The gene coding for Xyn11A was identified using PCR amplification with consensus primers. It was then fully sequenced to reveal an open reading frame of 1809 bp. The predicted N-terminal domain exhibited xylanolytic activity and was classed to the family 11 of glycosyl hydrolases; it is followed by a region with homology to a family 6 cellulose binding module. The C-terminal domain codes for a putative NodB-like polysaccharide deacetylase which is predicted to be an acetyl esterase implicated in debranching activity in the xylan backbone. As similar domain organization was also found in several other xylanases from a diverse range of bacteria, a common ancestor of such a xylanase is considered to be present and spread, possibly by horizontal gene transfer, to other microorganisms from different ecological niches.PUBLICATION ABSTRACT
We show that the on-shell effective theory (OSEFT) is the quantum field theory counterpart of a Foldy-Wouthuysen diagonalization of relativistic quantum mechanics for massless fermions. Thus, it is ...free of the Zitterbewegung oscillations that would yield an ill-defined meaning to the semiclassical transport approach at short distances if derived from the pure Dirac picture. We present a detailed derivation of the collision terms in the chiral kinetic theory using the OSEFT. Collision integrals are derived up to order 1 / E , where E is the energy of an on-shell fermion. At this order, the collision terms depend on the spin tensor of the fermion, and in the presence of chiral imbalance, it describes how a massless fermion of a given helicity interacts differently with the transverse photons of different circular polarization. In order to back up our results, we check that they allow us to reproduce the fermion decay rate in an ultradegenerate plasma with a chiral imbalance computed directly from QED.
There are no reliable official data available on tuberculosis (TB) in Spain.
To ascertain the epidemiological trends of TB in Spain from 1991-1999.
In an annual survey conducted by the Tuberculosis ...and Respiratory Infections (TRI) Working Group of the Spanish Society of Pneumology and Thoracic Surgery (SEPAR), data on tuberculosis disease and infection were solicited from two information sources: 1) the public health services of the 17 Autonomous Regions (AR), and 2) 60 TRI members in different parts of Spain.
TB incidence declined from 36.4/100,000 in 1991 to 26.7 in 1999 according to the AR (average annual decline 3.3%), and from 45.6 to 26.8 according to TRI members (annual decline 5.1%). A similar observation was made for smear-positive cases (AR annual decline: 3.0%; TRI: 5.6%). Tuberculosis infection at 6 years of age also decreased according to both information sources (AR: 0.87% in 1991 to 0.5% in 1998, annual decline 6%, and TRI members: 1.00% in 1991 and 0.9% in 1997, annual decline 4.2%).
The observed rates of TB are higher than stated in official figures. In spite of the decreasing trend, observed declines are small and the current rates continue to be among the highest among industrialised countries.
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