2,617 research outputs found
Isolation and Partial Analysis of Proteins and Polysaccharides of Rhizobium trifolii
The outer membrane and periplasmic proteins of Rhizobium trifolii ANU 843 and its mutants ANU 851 and ANU 845(pRt150) were isolated and analyzed by polyacrylamide gel electrophoresis (PAGE). ANU 843 is the wild type strain which possesses all the characteristics necessary for nitrogen fixation. ANU 851 has a transposon (Tn5) inserted into the nodD gene of the root hair curling region of the symbiotic plasmid. It has lost its ability to cause root hair curling and therefore can not form nodules and can not fix nitrogen. ANU 845(pRt150) harbors only the 5.5 kb root hair curling region of the pSym which is comprised of the genes nodD, A, B, C. The band profile of the outer membrane proteins from the three strains are similar. These proteins have molecular weights of 129, 48, 42, 38, 34,21, and 20 kDa. In the case of the periplasmic proteins, ANU 843 and 851 exhibit the same protein profile except for a 23.4 kDa protein present in 851 but missing in 843. ANU 845(pRt150), on the other hand, has a 38 kDa protein which is absent in both 843 and 851. Also it is missing the 22 and 28 kDa protein found in both 843 and 851.
A strain which contains the 14 kb nodulation region, ANU 845(pRt032), was exposed to inducing materials in order to study the expression of the nodulation genes. The optimum conditions for induction were determined by using a mu-lac mutant. ANU 845(pRt032)121 has a mu-lac inserted in nodA. When the root hair curling genes are expressed, mu-lac is simultaneously expressed, which leads to the production of B-galactosidase. Induction is thus measured by the extent of B-galactosidase activity. The maximum induction occurs at early log phase of bacterial growth.
The outer membrane, periplasmic and cytoplasmic proteins, extracellularpolyssacharides (EPS), and lipoplysaccharides (LPS) of induced and noninduced ANU 845(pRt032) were isolated and analyzed. The PAGE results indicate induction of the 30, 29, 19, 17, and 16 kDa outer membrane proteins. Several periplasmic proteins seemed to be induced by apigenin, with the major differences noted in the 87, 65, 56, 48, 32, and 20 kDa proteins. The profile of the cytoplasmic proteins of the induced and noninduced are similar except that there is an additional 19 kDa protein and an enhancement of the 18.6 kDa protein in the induced.
The EPS compositions of the induced and noninduced are similar, suggesting that EPS may not play a role in the root hair curling process. Some small differences were noted on the neutral components of the LPSs. Further work involving structural analysis needs to be done to learn the significance of those differences
Biotechnological applications of functional metagenomics in the food and pharmaceutical industries
peer-reviewedMicroorganisms are found throughout nature, thriving in a vast range of environmental conditions. The majority of them are unculturable or difficult to culture by traditional methods. Metagenomics enables the study of all microorganisms, regardless of whether they can be cultured or not, through the analysis of genomic data obtained directly from an environmental sample, providing knowledge of the species present, and allowing the extraction of information regarding the functionality of microbial communities in their natural habitat. Function-based screenings, following the cloning and expression of metagenomic DNA in a heterologous host, can be applied to the discovery of novel proteins of industrial interest encoded by the genes of previously inaccessible microorganisms. Functional metagenomics has considerable potential in the food and pharmaceutical industries, where it can, for instance, aid (i) the identification of enzymes with desirable technological properties, capable of catalyzing novel reactions or replacing existing chemically synthesized catalysts which may be difficult or expensive to produce, and able to work under a wide range of environmental conditions encountered in food and pharmaceutical processing cycles including extreme conditions of temperature, pH, osmolarity, etc; (ii) the discovery of novel bioactives including antimicrobials active against microorganisms of concern both in food and medical settings; (iii) the investigation of industrial and societal issues such as antibiotic resistance development. This review article summarizes the state-of-the-art functional metagenomic methods available and discusses the potential of functional metagenomic approaches to mine as yet unexplored environments to discover novel genes with biotechnological application in the food and pharmaceutical industries.Science Foundation Ireland(SFI)Grant Number 13/SIRG/215
The Delta-Delta Intermediate State in 1S0 Nucleon-Nucleon Scattering From Effective Field Theory
We examine the role of the Delta-Delta intermediate state in low energy NN
scattering using effective field theory. Theories both with and without pions
are discussed. They are regulated with dimensional regularization and MSbar
subtraction. We find that the leading effects of the Delta-Delta state can be
absorbed by a redefinition of the contact terms in a theory with nucleons only.
It does not remove the requirement of a higher dimension operator to reproduce
data out to moderate momentum. The explicit decoupling of the Delta-Delta state
is shown for the theory without pions.Comment: 16 pages, 3 figures, uses harvma
Regularization, Renormalization and Range: The Nucleon-Nucleon Interaction from Effective Field Theory
Regularization and renormalization is discussed in the context of low-energy
effective field theory treatments of two or more heavy particles (such as
nucleons). It is desirable to regulate the contact interactions from the outset
by treating them as having a finite range. The low energy physical observables
should be insensitive to this range provided that the range is of a similar or
greater scale than that of the interaction. Alternative schemes, such as
dimensional regularization, lead to paradoxical conclusions such as the
impossibility of repulsive interactions for truly low energy effective theories
where all of the exchange particles are integrated out. This difficulty arises
because a nonrelativistic field theory with repulsive contact interactions is
trivial in the sense that the matrix is unity and the renormalized coupling
constant zero. Possible consequences of low energy attraction are also
discussed. It is argued that in the case of large or small scattering lengths,
the region of validity of effective field theory expansion is much larger if
the contact interactions are given a finite range from the beginning.Comment: 7 page
Renormalization of Singlet NN-Scattering with One Pion Exchange and Boundary Conditions
We present a simple and physically compelling boundary condition
regularization scheme in the framework of effective field theory as applied to
nucleon-nucleon interaction. It is free of off-shell ambiguities and
ultraviolet divergences and provides finite results at any step of the
calculation. Low energy constants and their non-perturbative evolution can
directly be obtained from experimental threshold parameters in a completely
unique and model independent way when the long range explicit pion effects are
removed. This allows to compute scattering phase shifts which are, by
construction consistent with effective range expansion to a given order in the
CM momentum and are free from finite cut-off artifacts. We illustrate how the
method works in the channel for the One Pion Exchange potential.Comment: (Latex, epsfig) 7 pages, 2 figure
Complex collective states in a one-dimensional two-atom system
We consider a pair of identical two-level atoms interacting with a scalar
field in one dimension, separated by a distance . We restrict our
attention to states where one atom is excited and the other is in the ground
state, in symmetric or anti-symmetric combinations. We obtain exact collective
decaying states, belonging to a complex spectral representation of the
Hamiltonian. The imaginary parts of the eigenvalues give the decay rates, and
the real parts give the average energy of the collective states. In one
dimension there is strong interference between the fields emitted by the atoms,
leading to long-range cooperative effects. The decay rates and the energy
oscillate with the distance . Depending on , the decay rates
will either decrease, vanish or increase as compared with the one-atom decay
rate. We have sub- and super-radiance at periodic intervals. Our model may be
used to study two-cavity electron wave-guides. The vanishing of the collective
decay rates then suggests the possibility of obtaining stable configurations,
where an electron is trapped inside the two cavities.Comment: 14 pages, 14 figures, submitted to Phys. Rev.
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