Complete genome sequence of new bacteriophage phiE142, which causes simultaneously lysis of multidrug-resistant Escherichia coli O157:H7 and Salmonella enterica

Bacterial strains used in the host range spectrum of the bacteriophage phiE142. Phage was assessed for host range by spot testing. (+) indicate positive sensitivity to phage lysis, and (-) indicate negative sensitivity to phage lysis. (DOCX 41 kb

Theoretical investigation of the structures of unsupported 38-atom CuPt clusters

A genetic algorithm has been used to perform a global sampling of the potential energy surface in the search for the lowest-energy structures of unsupported 38-atom Cu–Pt clusters. Structural details of bimetallic Cu–Pt nanoparticles are analyzed as a function of their chemical composition and the parameters of the Gupta potential, which is used to mimic the interatomic interactions. The symmetrical weighting of all parameters used in this work strongly influences the chemical ordering patterns and, consequently, cluster morphologies. The most stable structures are those corresponding to potentials weighted toward Pt characteristics, leading to Cu–Pt mixing for a weighting factor of 0.7. This reproduces density functional theory (DFT) results for Cu–Pt clusters of this size. For several weighting factor values, the Cu30Pt8 cluster exhibits slightly higher relative stability. The copper-rich Cu32Pt6 cluster was reoptimized at the DFT level to validate the reliability of the empirical approach, which predicts a Pt@Cu core-shell segregated cluster. A general increase of interatomic distances is observed in the DFT calculations, which is greater in the Pt core. After cluster relaxation, structural changes are identified through the pair distribution function. For the majority of weighting factors and compositions, the truncated octahedron geometry is energetically preferred at the Gupta potential level of theory

Cu-Doped KCl folded and unfolded band structure and optical properties studied by DFT calculations

We computed the optical properties and the folded and unfolded band structure of Cu-doped KCl crystals. The calculations use the plane-wave pseudo-potential approach implemented in the ABINIT electronic structure package within the first-principles density-functional theory framework. Cu substitution into pristine KCl crystals requires calculation by the supercell (SC) method from a theoretical perspective. This procedure shrinks the Brillouin zone, resulting in a folded band structure that is difficult to interpret. To solve this problem and gain insight into the effect of cuprous ion (Cu+) on electronic properties; We unfolded the band structure of SC KCl:Cu to directly compare with the band structure of the primitive cell (PC) of pristine KCl. To understand the effect of Cu substitution on optical absorption, we calculated the imaginary part of the dielectric function of KCl:Cu through a sum-over-states formalism and broke it down into different band contributions by partially making an iterated cumulative sum (ICS) of selected valence and conduction bands. As a result, we identified those interband transitions that give rise to the absorption peaks due to the Cu ion. These transitions include valence and conduction bands formed by the Cu-3d and Cu-4s electronic states. To investigate the effects of doping position, we consider different doping positions, where the Cu dopant occupies all the substitutional sites replacing host K cations. Our results indicate that the doping position's effects give rise to two octahedral shapes in the geometric structure. The distorted-twisted octahedral square bipyramidal geometric-shape induces a difference in the crystal field splitting energy compared to that of the perfect octahedral square bipyramidal geometric-shape.Comment: 39 total pages, 30 article, and 9 references. There are 19 figures done with gnuplot high-qualit

Isolation and Characterization of phiLLS, a Novel Phage with Potential Biocontrol Agent against Multidrug-Resistant Escherichia coli

Foodborne diseases are a serious and growing problem, and the incidence and prevalence of antimicrobial resistance among foodborne pathogens is reported to have increased. The emergence of antibiotic-resistant bacterial strains demands novel strategies to counteract this epidemic. In this regard, lytic bacteriophages have reemerged as an alternative for the control of pathogenic bacteria. However, the effective use of phages relies on appropriate biological and genomic characterization. In this study, we present the isolation and characterization of a novel bacteriophage named phiLLS, which has shown strong lytic activity against generic and multidrug-resistant Escherichia coli strains. Transmission electron microscopy of phiLLS morphology revealed that it belongs to the Siphoviridae family. Furthermore, this phage exhibited a relatively large burst size of 176 plaque-forming units per infected cell. Phage phiLLS significantly reduced the growth of E. coli under laboratory conditions. Analyses of restriction profiles showed the presence of submolar fragments, confirming that phiLLS is a pac-type phage. Phylogenetic analysis based on the amino acid sequence of large terminase subunits confirmed that this phage uses a headful packaging strategy to package their genome. Genomic sequencing and bioinformatic analysis showed that phiLLS is a novel bacteriophage that is most closely related to T5-like phages. In silico analysis indicated that the phiLLS genome consists of 107,263 bp (39.0 % GC content) encoding 160 putative ORFs, 16 tRNAs, several potential promoters and transcriptional terminators. Genome analysis suggests that the phage phiLLS is strictly lytic without carrying genes associated with virulence factors and/or potential immunoreactive allergen proteins. The bacteriophage isolated in this study has shown promising results in the biocontrol of bacterial growth under in vitro conditions, suggesting that it may prove useful as an alternative agent for the control of foodborne pathogens. However, further oral toxicity testing is needed to ensure the safety of phage use

Characterization of novel bacteriophage phiC119 capable of lysing multidrug-resistant Shiga toxin-producing Escherichia coli O157:H7

Background Shiga toxin-producing Escherichia coli (STEC) is one of the most common and widely distributed foodborne pathogens that has been frequently implicated in gastrointestinal and urinary tract infections. Moreover, high rates of multiple antibiotic-resistant E. coli strains have been reported worldwide. Due to the emergence of antibiotic-resistant strains, bacteriophages are considered an attractive alternative to biocontrol pathogenic bacteria. Characterization is a preliminary step towards designing a phage for biocontrol. Methods In this study, we describe the characterization of a bacteriophage designated phiC119, which can infect and lyse several multidrug-resistant STEC strains and some Salmonella strains. The phage genome was screened to detect the stx-genes using PCR, morphological analysis, host range was determined, and genome sequencing were carried out, as well as an analysis of the cohesive ends and identification of the type of genetic material through enzymatic digestion of the genome. Results Analysis of the bacteriophage particles by transmission electron microscopy showed that it had an icosahedral head and a long tail, characteristic of the family Siphoviridae. The phage exhibits broad host range against multidrug-resistant and highly virulent E. coli isolates. One-step growth experiments revealed that the phiC119 phage presented a large burst size (210 PFU/cell) and a latent period of 20 min. Based on genomic analysis, the phage contains a linear double-stranded DNA genome with a size of 47,319 bp. The phage encodes 75 putative proteins, but lysogeny and virulence genes were not found in the phiC119 genome. Conclusion These results suggest that phage phiC119 may be a good biological control agent. However, further studies are required to ensure its control of STEC and to confirm the safety of phage use

Recubrimientos para heridas con Aloe-gel combinado con alginato, pectina y quitosano: aplicaciones in vivo

Skin wound healing is a complex process that involves different interrelated phases (hemostasis, inflammation, proliferation and remodeling). Aloe-gel (AG) has been considered as a biomaterial that contributes to the modulation, regeneration and acceleration in damaged tissue, during the regeneration process; it is also recommended for burn and superficial skin wounds treatments. AG also has been considered as an important biomaterial for the elaboration of wound healing dressing. However, the direct application of AG on wounds has showed some disadvantages such as: dehydration, rapid oxidation in phytoconstituent and low proportion of solutes. The AG incorporation into polysaccharides matrix (alginate, pectin and chitosan) is a strategy used to keep the biological activity and functional compounds. Even though, there are some biomaterials that have been elaborated with these polysaccharides mixtures as proposal for wound healing dressing, their applications in animal models have been limited. Therefore, this review has as aim to document the development of wound healing dressings with AG, incorporated in polysaccharides matrix, and its effect on the wounds healing. La recuperación de las heridas en la piel es un proceso complejo e interrelacionado que se desarrolla a través de varias fases (hemostasia, inflamatoria, proliferativa y remodelación). El Aloe-gel (AG) ha sido considerado un biomaterial que puede coadyuvar en la modulación, regeneración y aceleración de la recuperación del tejido celular dañado e incluso se ha recomendado para su aplicación en heridas o quemaduras superficiales de tipo cutáneas.Debido a lo anterior, se ha promovido el uso del AG como un importante biomaterial que puede ser utilizado en la fabricación de recubrimientos para heridas (RH). Sin embargo, su aplicación directa sobre las heridas presenta desventajas, ya que puede inducir a deshidratación en la zona, rápida oxidación de sus fitoconstituyentes y baja proporción de solutos. Una estrategia que puede ayudar a conservar su actividad biológica y a sus componentes inalterados y funcionales, es su incorporación hacia matrices de polisacáridos como el alginato, pectina y quitosano. Aunque existen ya algunos biomateriales de esta mezcla que se han propuestos como RH, su aplicación en modelos in vivo es aún limitado. Por lo anterior, la presente revisión pretende documentar el desarrollo de RH con AG incorporado en polisacáridos y sus efectos en la recuperación de heridas in vivo

Cromatografía de interacción hidrofóbica como método de separación de proteasas alcalinas de vísceras de Scomberomorus sierra

This study focused on recovering alkaline proteases from the viscera of Scomberomorus sierra through hydrophobic interaction chromatography. Three alkaline proteases were partially separated using this chromatographic technique; two of them, with molecular weights of 19 and 31 kDa, were identified as trypsin-like enzymes according to inhibition assays. The 31 kDa alkaline protease, the only isolated enzyme, was purified under following chromatographic conditions: ammonium sulfate 13% (w/v) and ethylene glycol 27% (w/v); this enzyme showed maximum activity at pH 9 – 10 and 50 – 60 °C and was strongly inhibited by soybean trypsin inhibitor (SBTI) and porcine trypsin inhibitor (TPI). A third alkaline protease with molecular weight of 20 kDa was partially separated and inhibited by tosyl phenylalanyl chloromethyl ketone (TPCK), showing optimum activity at pH 9 – 11 and 60 °C. These results show that the viscera of Scomberomorus sierra may be useful as source of proteases.Este estudio se enfocó en recuperar proteasas alcalinas de vísceras de Scomberomorus sierra  mediante cromatografía de interacción hidrofóbica. Tres proteasas alcalinas se lograron separar parcialmente usando esta técnica cromatográfica; dos de ellas con pesos moleculares de 19 y 31 kDa fueron identificadas como enzimas tipo tripsina de acuerdo a ensayos de inhibición. La proteasa alcalina con peso molecular de 31 kDa, única enzima aislada, fue purificada bajo las siguientes condiciones cromatográficas: sulfato de amonio l3% (p/v) y etilenglicol al 27% (p/v); esta enzima mostró actividad máxima a pH 9 – 10 y 50 – 60 °C y fue fuertemente inhibida por el inhibidor de tripsina de soya (SBTI) como por el inhibidor de tripsina porcina (TPI). Una tercera proteasa alcalina con peso molecular de 20 kDa fue parcialmente separada e inhibida por tosil fenilalanil clorometil cetona (TPCK), la cual mostró actividad óptima a pH 9 – 11 y 60 °C. Estos resultados muestran que las vísceras de Scomberomorus sierra podrían ser de utilidad como fuente de proteasas