1,761 research outputs found
Mapping the tail fiber as the receptor binding protein responsible for differential host specificity of Pseudomonas aeruginosa bacteriophages PaP1 and JG004.
The first step in bacteriophage infection is recognition and binding to the host receptor, which is mediated by the phage receptor binding protein (RBP). Different RBPs can lead to differential host specificity. In many bacteriophages, such as Escherichia coli and Lactococcal phages, RBPs have been identified as the tail fiber or protruding baseplate proteins. However, the tail fiber-dependent host specificity in Pseudomonas aeruginosa phages has not been well studied. This study aimed to identify and investigate the binding specificity of the RBP of P. aeruginosa phages PaP1 and JG004. These two phages share high DNA sequence homology but exhibit different host specificities. A spontaneous mutant phage was isolated and exhibited broader host range compared with the parental phage JG004. Sequencing of its putative tail fiber and baseplate region indicated a single point mutation in ORF84 (a putative tail fiber gene), which resulted in the replacement of a positively charged lysine (K) by an uncharged asparagine (N). We further demonstrated that the replacement of the tail fiber gene (ORF69) of PaP1 with the corresponding gene from phage JG004 resulted in a recombinant phage that displayed altered host specificity. Our study revealed the tail fiber-dependent host specificity in P. aeruginosa phages and provided an effective tool for its alteration. These contributions may have potential value in phage therapy
Scaling law for three-body collisions near a narrow s-wave Feshbach resonance
Ultracold atomic gases provide a controllable system to study the inelastic
processes for three-body systems, where the three-body recombination rate
depends on the scattering length scaling. Such scalings have been confirmed in
bosonic systems with various interaction strengths, but their existence with
fermionic atoms remains elusive. In this work, we report on an experimental
investigation of the scaling law for the three-body atomic loss rate in a
two-component Li Fermi gas with the scattering length . The scaling
law is validated within a certain range of near the narrow -wave
Feshbach resonance, where , and is the gas
temperature. The scaling law is observed to have an upper and a lower bound in
terms of the scattering length. For the upper bound, when , the power-law scaling is suppressed by the unitary behavior of the
resonance caused by the strong three-body collisions. For the lower bound,
, the finite range effect modifies the scaling law by the
effective scattering length . These results indicate that the three-body
recombination rate in a fermionic system could be characterized by the scaling
law associated with the generalized Efimov physics.Comment: 11 pages, 3 figures, 1 tabl
Chromosomal DNA deletion confers phage resistance to Pseudomonas aeruginosa.
Bacteria develop a broad range of phage resistance mechanisms, such as prevention of phage adsorption and CRISPR/Cas system, to survive phage predation. In this study, Pseudomonas aeruginosa PA1 strain was infected with lytic phage PaP1, and phage-resistant mutants were selected. A high percentage (~30%) of these mutants displayed red pigmentation phenotype (Red mutant). Through comparative genomic analysis, one Red mutant PA1r was found to have a 219.6 kb genomic fragment deletion, which contains two key genes hmgA and galU related to the observed phenotypes. Deletion of hmgA resulted in the accumulation of a red compound homogentisic acid; while A galU mutant is devoid of O-antigen, which is required for phage adsorption. Intriguingly, while the loss of galU conferred phage resistance, it significantly attenuated PA1r in a mouse infection experiment. Our study revealed a novel phage resistance mechanism via chromosomal DNA deletion in P. aeruginosa
Holographic Storage of Biphoton Entanglement
Coherent and reversible storage of multi-photon entanglement with a multimode
quantum memory is essential for scalable all-optical quantum information
processing. Although single photon has been successfully stored in different
quantum systems, storage of multi-photon entanglement remains challenging
because of the critical requirement for coherent control of photonic
entanglement source, multimode quantum memory, and quantum interface between
them. Here we demonstrate a coherent and reversible storage of biphoton
Bell-type entanglement with a holographic multimode atomic-ensemble-based
quantum memory. The retrieved biphoton entanglement violates Bell's inequality
for 1 microsecond storage time and a memory-process fidelity of 98% is
demonstrated by quantum state tomography.Comment: 5 pages, 4 figures, accepted by Phys. Rev. Let
A generic framework for genuine multipartite entanglement detection
Design of detection strategies for multipartite entanglement stands as a
central importance on our understanding of fundamental quantum mechanics and
has had substantial impact on quantum information applications. However,
accurate and robust detection approaches are severely hindered, particularly
when the number of nodes grows rapidly like in a quantum network. Here we
present an exquisite procedure that generates novel entanglement witness for
arbitrary targeted state via a generic and operational framework. The framework
enjoys a systematic and high-efficient character and allows to substantiate
genuine multipartite entanglement for a variety of states that arise naturally
in practical situations, and to dramatically outperform currently standard
methods. With excellent noise tolerance, our framework should be broadly
applicable to witness genuine multipartite entanglement in various practically
scenarios, and to facilitate making the best use of entangled resources in the
emerging area of quantum network.Comment: 27 pages, 5 figure
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