Specific detection of Salmonella enterica and Escherichia coli strains by using ELISA with bacteriophages as recognition agents

The use of bacteriophages, instead of antibodies, in the ELISA-based detection of bacterial strains was tested. This procedure appeared to be efficient, and specific strains of Salmonella enterica and Escherichia coli could be detected. The sensitivity of the assay was about 105 bacterial cells/well (106/ml), which is comparable with or outperforms other ELISA tests detecting intact bacterial cells without an enrichment step. The specificity of the assay depends on the kind of bacteriophage used. We conclude that the use of bacteriophages in the detection and identification of bacteria by an ELISA-based method can be an alternative to the use of specific antibodies. The advantages of the use of bacteriophages are their environmental abundance (and, thus, a possibility to isolate various phages with different specificities) and the availability of methods for obtaining large amounts of phage lysates, which are simple, rapid, cheap, and easy

Influence of the Escherichia coli oxyR gene function on λ prophage maintenance

In Escherichia coli hosts, hydrogen peroxide is one of the factors that may cause induction of λ prophage. Here, we demonstrate that H2O2-mediated λ prophage induction is significantly enhanced in the oxyR mutant host. The mRNA levels for cI gene expression were increased in a λ lysogen in the presence of H2O2. On the other hand, stimulation of the pM promoter by cI857 overproduced from a multicopy plasmid was decreased in the ΔoxyR mutant in the presence of H2O2 but not under normal growth conditions. The purified OxyR protein did bind specifically to the pM promoter region. This binding impaired efficiency of interaction of the cI protein with the OR3 site, while stimulating such a binding to OR2 and OR1 sites, in the regulatory region of the pM promoter. We propose that changes in cI gene expression, perhaps in combination with moderately induced SOS response, may be responsible for enhanced λ prophage induction by hydrogen peroxide in the oxyR mutant. Therefore, OxyR seems to be a factor stimulating λ prophage maintenance under conditions of oxidative stress. This proposal is discussed in the light of efficiency of induction of lambdoid prophages bearing genes coding for Shiga toxins

V*-algebras, independence algebras and logic

Independence algebras were introduced in the early 1990s by specialists in semigroup theory, as a tool to explain similarities between the transformation monoid on a set and the endomorphism monoid of a vector space. It turned out that these algebras had already been defined and studied in the 1960s, under the name of v*-algebras, by specialists in universal algebra (and statistics). Our goal is to complete this picture by discussing how, during the middle period, independence algebras began to play a very important role in logic

Characterizing RecA-Independent Induction of Shiga toxin2-Encoding Phages by EDTA Treatment

Background: The bacteriophage life cycle has an important role in Shiga toxin (Stx) expression. The induction of Shiga toxin-encoding phages (Stx phages) increases toxin production as a result of replication of the phage genome, and phage lysis of the host cell also provides a means of Stx toxin to exit the cell. Previous studies suggested that prophage induction might also occur in the absence of SOS response, independently of RecA. Methodology/Principal Findings: The influence of EDTA on RecA-independent Stx2 phage induction was assessed, in laboratory lysogens and in EHEC strains carrying Stx2 phages in their genome, by Real-Time PCR. RecA-independent mechanisms described for phage l induction (RcsA and DsrA) were not involved in Stx2 phage induction. In addition, mutations in the pathway for the stress response of the bacterial envelope to EDTA did not contribute to Stx2 phage induction. The effect of EDTA on Stx phage induction is due to its chelating properties, which was also confirmed by the use of citrate, another chelating agent. Our results indicate that EDTA affects Stx2 phage induction by disruption of the bacterial outer membrane due to chelation of Mg 2+. In all the conditions evaluated, the pH value had a decisive role in Stx2 phage induction. Conclusions/Significance: Chelating agents, such as EDTA and citrate, induce Stx phages, which raises concerns due to their frequent use in food and pharmaceutical products. This study contributes to our understanding of the phenomenon o

Prevalence of antibodies against Neospora caninum in dogs from urban areas in Central Poland

Neospora caninum is a protozoan parasite which causes abortion in cattle as well as reproduction problems and neurological disorders in dogs. To assess the prevalence of the parasite in urban dogs in the Mazovian Voivodeship, Central Poland, serum samples from 257 dogs were analyzed for the presence of specific IgG antibodies. The examined dogs visited three private veterinary clinics located in Warsaw due to control tests, vaccinations, or other reasons not directly connected with neosporosis. Using ELISA and Western blot, antibodies against the parasite were detected in 56 out of 257 dogs, giving a prevalence of 21.7%. A greater prevalence was observed in female dogs than in males, 28% and 17.3%, respectively, and the differences were statistically significant (p < 0.05). There were no significant differences in seroprevalence of Neospora infection within the age groups (p > 0.05). This study indicates the presence of N. caninum in the Mazovian Voivodeship, in dogs which live in urban areas and exposure of these dogs to the parasite. The fact that seropositive dogs had no contact with cattle confirms the important role of dogs in the parasite’s epidemiology

A reliable method for storage of tailed phages

A universal and effective method for long-term storage of bacteriophages has not yet been described. We show that randomly selected tailed phages could be stored inside the infected cells at−80 °C without a major loss of phage and host viability. Our results suggest the suitability of this method as a standard for phage preservation

Study of Adsorption Properties on Lithium Doped Activated Carbon Materials

A volumetric method was applied to study an adsorption coefficient of hydrogen molecules in a gas phase on super activated carbon surface. The investigations were focused on getting the best possible materials for the energy storage. Several treatments on raw samples were used to improve adsorption properties. The biggest capacities were obtained after high temperature treatment at reduced atmosphere. The adsorption coefficient at 77 K and 2 MPa amounts to 3.158 wt%. The charge transfer between lithium and carbon surface groups via the doping reaction enhanced the energy of adsorption. It was also found that there is a gradual decrease in the adsorbed amount of H$\text{}_{2}$ molecules due to occupation active sites by lithium ions

EPR and Impedance Measurements of Graphene Oxide and Reduced Graphene Oxide

We report the observations of electron paramagnetic resonance and impedance measurements of graphene oxide and reduced graphene oxide performed in the wide temperature range in order to get insight into the electronic properties of graphene-based materials and the role of oxygen functionalities in the charge carrier transport phenomena. In such systems the strong spin localization, hopping charge carrier transport as well as the formation of adsorption layers are observed, all the phenomena changing significantly after the heavily oxidized graphene is reduced