Bacteriophage-Resistant Mutants in Yersinia pestis: Identification of Phage Receptors and Attenuation for Mice

Background: Bacteriophages specific for Yersinia pestis are routinely used for plague diagnostics and could be an alternative to antibiotics in case of drug-resistant plague. A major concern of bacteriophage therapy is the emergence of phageresistant mutants. The use of phage cocktails can overcome this problem but only if the phages exploit different receptors. Some phage-resistant mutants lose virulence and therefore should not complicate bacteriophage therapy. Methodology/Principal Findings: The purpose of this work was to identify Y. pestis phage receptors using site-directed mutagenesis and trans-complementation and to determine potential attenuation of phage-resistant mutants for mice. Six receptors for eight phages were found in different parts of the lipopolysaccharide (LPS) inner and outer core. The receptor for R phage was localized beyond the LPS core. Most spontaneous and defined phage-resistant mutants of Y. pestis were attenuated, showing increase in LD 50 and time to death. The loss of different LPS core biosynthesis enzymes resulted in the reduction of Y. pestis virulence and there was a correlation between the degree of core truncation and the impact on virulence. The yrbH and waaA mutants completely lost their virulence. Conclusions/Significance: We identified Y. pestis receptors for eight bacteriophages. Nine phages together use at least seven different Y. pestis receptors that makes some of them promising for formulation of plague therapeutic cocktails. Most phage-resistant Y. pestis mutants become attenuated and thus should not pose a serious problem for bacteriophag

method of forming lattice matched layer over a surface of a silicon substrate

A method of forming lattice matched single crystal wide bandgap II-VI compound semiconductor films over a silicon substrate includes first cleaning (10) the silicon substrate. A passivation layer is formed (18), which may comprise arsenic, germanium, or CaF2, among others. The lattice matched layer is then grown (26) on the passivation layer.U

method of forming lattice matched layer over a surface of a silicon substrate

A method of forming lattice matched single crystal wide bandgap II-VI compound semiconductor films over a silicon substrate includes first cleaning (10) the silicon substrate. A passivation layer is formed (18), which may comprise arsenic, germanium, or CaF2, among others. The lattice matched layer is then grown (26) on the passivation layer.U

Method of forming lattice matched layer over a surface of a silicon substrate

A method of forming lattice matched single crystal wide bandgap II-VI compound semiconductor films over a silicon substrate includes first cleaning (10) the silicon substrate. A passivation layer is formed (18), which may comprise arsenic, germanium, or CaF2, among others. The lattice matched layer is then grown (26) on the passivation layer.U

Behaviour of group IIIA impurities in PbTe: implications to improve thermoelectric efficiency

We investigated the impact of doping group IIIA elements (Al, Ga, In and Tl) on the electronic structure and stability of PbTe by first principles calculations. The impurity-induced defect level changes as a function of the charge state of the impurity. We find that Al and In prefer to act as donors while Ga and Tl tend to act as acceptors in PbTe. Our analysis supports the ‘impurity level’ model where an impurity-induced localized state overlaps either the conduction band or valence band of PbTe, but our results do not agree with ‘mix-valence’ (i.e. 2In2+ → In+ + In3+) or ‘auto-compensation’ (i.e. 2In0 → In+ + In−) models. Our calculations suggest that Tl and In are suitable dopants for improving the thermoelectric efficiency through enhancing the Seebeck coefficient for p- and n-type PbTe, respectively.</jats:p