Biodiversity of bacteriophages: morphological and biological properties of a large group of phages isolated from urban sewage

A large scale analysis presented in this article focuses on biological and physiological variety of bacteriophages. A collection of 83 bacteriophages, isolated from urban sewage and able to propagate in cells of different bacterial hosts, has been obtained (60 infecting Escherichia coli, 10 infecting Pseudomonas aeruginosa, 4 infecting Salmonella enterica, 3 infecting Staphylococcus sciuri, and 6 infecting Enterococcus faecalis). High biological diversity of the collection is indicated by its characteristics, both morphological (electron microscopic analyses) and biological (host range, plaque size and morphology, growth at various temperatures, thermal inactivation, sensitivity to low and high pH, sensitivity to osmotic stress, survivability upon treatment with organic solvents and detergents), and further supported by hierarchical cluster analysis. By the end of the research no larger collection of phages from a single environmental source investigated by these means had been found. The finding was confirmed by whole genome analysis of 7 selected bacteriophages. Moreover, particular bacteriophages revealed unusual biological features, like the ability to form plaques at low temperature (4 °C), resist high temperature (62 °C or 95 °C) or survive in the presence of an organic solvents (ethanol, acetone, DMSO, chloroform) or detergent (SDS, CTAB, sarkosyl) making them potentially interesting in the context of biotechnological applications

Characterization of Bacteriophage vB-EcoS-95, Isolated From Urban Sewage and Revealing Extremely Rapid Lytic Development

Morphological, biological, and genetic characteristics of a virulent Siphoviridae phage, named vB-EcoS-95, is reported. This phage was isolated from urban sewage. It was found to infect some Escherichia coli strains giving clear plaques. The genome of this phage is composed of 50,910 bp and contains 89 ORFs. Importantly, none of the predicted ORFs shows any similarity with known pathogenic factors that would prevent its use in medicine. Genome sequence analysis of vB-EcoS-95 revealed 74% similarity to genomic sequence of Shigella phage pSf-1. Compared to pSf-1, phage vb-EcoS-95 does not infect Shigella strains and has an efficient bacteriolytic activity against some E. coli strains. One-step growth analysis revealed that this phage has a very short latent period (4 min), and average burst size of 115 plaque forming units per cell, which points to its high infectivity of host cells and strong lytic activity. The bacteriolytic effect of vB-EcoS-95 was tested also on biofilm-producing strains. These results indicate that vB-EcoS-95 is a newly discovered E. coli phage that may be potentially used to control the formation of biofilms

Prospects for biocontrol of Vibrio parahaemolyticus contamination in blue mussels (Mytilus edulus) – a year-long study

Vibrio parahaemolyticus is an environmental organism normally found in subtropical estuarine environments which can cause seafood-related human infections. Clinical disease is associated with diagnostic presence of tdh and/or trh virulence genes and identification of these genes in our preliminary isolates from retail shellfish prompted a year-long surveillance of isolates from a temperate estuary in the north of England. The microbial and environmental analysis of 117 samples of mussels, seawater or sediment showed the presence of V. parahaemolyticus from mussels (100%) at all time-points throughout the year including the colder months although they were only recovered from 94.9% of seawater and 92.3% of sediment samples. Throughout the surveillance, 96 isolates were subjected to specific PCR for virulence genes and none tested positive for either. The common understanding that consuming poorly cooked mussels only represents a risk of infection during summer vacations therefore is challenged. Further investigations with V. parahaemolyticus using RAPD-PCR cluster analysis showed a genetically diverse population. There was no distinct clustering for ‘environmental’ or 'clinical reference strains although a wide variability and heterogeneity agreed with other reports. Continued surveillance of isolates to allay public health risks are justified since geographical distribution and composition of V. parahaemolyticus varies with future ocean warming and the potential of environmental strains to acquire virulence genes from pathogenic isolates. The prospects for intervention by phage-mediated biocontrol to reduce or eradicate V. parahaemolyticus in mussels was also investigated. Bacteriophages isolated from enriched samples collected from the river Humber were assessed for their ability to inhibit the growth of V. parahaemolyticus strains in-vitro and in-vivo (with live mussels). V. parahaemolyticus were significantly reduced in-vitro, by an average of 1 log - 2 log units and in-vivo, significant reduction of the organisms in mussels occurred in 3 replicate experimental tank set ups with a ‘phage cocktail’ containing 12 different phages. Our perspective biocontrol study suggests that a cocktail of specific phages targeted against strains of V. parahaemolyticus provides good evidence in an experimental setting of the valuable potential of phage as a decontamination agent in natural or industrial mussel processing

Recombination Events in Putative Tail Fibre Gene in Litunavirus Phages Infecting Pseudomonas aeruginosa and Their Phylogenetic Consequences

Recombination is the main driver of bacteriophage evolution. It may serve as a tool for extending the phage host spectrum, which is significant not only for phages’ ecology but also for their utilisation as therapeutic agents of bacterial infections. The aim of this study was to detect the recombination events in the genomes of Litunavirus phages infecting Pseudomonas aeruginosa, and present their impact on phylogenetic relations within this phage group. The phylogenetic analyses involved: the whole-genome, core-genome (Schitoviridae conserved genes), variable genome region, and the whole-genome minus variable region. Interestingly, the recombination events taking place in the putative host recognition region (tail fibre protein gene and the adjacent downstream gene) significantly influenced tree topology, suggesting a strong phylogenetic signal. Our results indicate the recombination between phages from two genera Litunavirus and Luzeptimavirus and demonstrate its influence on phage phylogeny

Recombination events in putative tail fibre gene in Litunavirus phages infecting Pseudomonas aeruginosa

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Revision of Gyrodactylus salaris phylogeny inspired by new evidence for Eemian crossing between lineages living on grayling in Baltic and White sea basins

In this research, grayling-specific Gyrodactylus salaris Malmberg, 1957 isolates from Baltic Sea basin were collected in Sweden for the first time. Samples were obtained in three drainage systems: Kalixälven (River Kaitum), Ljungan (River Sölvbacka strömmar), and Umeälven (River Juktån). Three molecular markers were analysed: nuclear ITS rDNA (Internal Transcribed Spacer) and ADNAM1 (Anonymous DNA Marker 1), and mitochondrial cox1 gene. As a result, four new mitochondrial haplotypes were identified (III-C1tt, III-C1ttht, IX-A1tt and X-A1tt). The ADNAM1 analyses resulted in revealing two new alleles (WS4 and BS9) and two new genotypes (T6 and T7). T7 seems to be an indicator of ancient crossing between Baltic and White Sea lineages of the parasite which happened during a first 3000-year period of Eemian interglacial about 130,000 years ago in the connection between Baltic and White Sea. Molecular clock estimates were adjusted, revealing the mean substitution rate and the divergence rate among branches of 3.6% (95% HPD: 2.2%–5.2%) and 7.2% per million years, respectively. As a result, cox1 phylogeny rooted with the introgressed haplotypes has been revised and altered in accordance to new data, revealing fourteen equidistant lineages five of which have been excluded from the study. Based on the new phylogenetic approach, including the molecular clock, this work suggests an overall revision of G. salaris phylogeny and attempts at precisely drawing the division of lineages within this polytypic species as well as proposes unification in nomenclature for its strains

Microstructural and Fractographic Analysis of Plastically Deformed Al-Zn-Mg Alloy Subjected to Combined High-Cycle Bending-Torsion Fatigue

The present manuscript aims to determine the effect of various deformation levels during low-temperature thermo-mechanical treatment (LTTT) on the microstructure and fatigue strength of Zr-microalloyed Al-Zn-Mg alloy. The fatigue strength of the alloy was studied in high-cycle bending-torsion tests. The determination of the influence of plastic deformation level during LTTT on the microstructure was based on transmission electron microscopy (TEM) observations. The analysis of fracture after the fatigue tests was performed based on fractographic images using scanning electron microscopy (SEM). It was found that the major factor affecting the microstructure of the alloy, and determining the nature of fatigue fracture, is the strain level applied during LTTT

Characteristics of a Series of Three Bacteriophages Infecting Salmonella enterica Strains

Molecular and functional characterization of a series of three bacteriophages, vB_SenM-1, vB_SenM-2, and vB_SenS-3, infecting various Salmonella enterica serovars and strains is presented. All these phages were able to develop lytically while not forming prophages. Moreover, they were able to survive at pH 3. The phages revealed different host ranges within serovars and strains of S. enterica, different adsorption rates on host cells, and different lytic growth kinetics at various temperatures (in the range of 25 to 42 &deg;C). They efficiently reduced the number of cells in the bacterial biofilm and decreased the biofilm mass. Whole genome sequences of these phages have been determined and analyzed, including their phylogenetic relationships. In conclusion, we have demonstrated detailed characterization of a series of three bacteriophages, vB_SenM-1, vB_SenM-2, and vB_SenS-3, which reveal favorable features in light of their potential use in phage therapy of humans and animals, as well as for food protection purposes