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

The influence of the accessory genome on bacterial pathogen evolution

Bacterial pathogens exhibit significant variation in their genomic content of virulence factors. This reflects the abundance of strategies pathogens evolved to infect host organisms by suppressing host immunity. Molecular arms-races have been a strong driving force for the evolution of pathogenicity, with pathogens often encoding overlapping or redundant functions, such as type III protein secretion effectors and hosts encoding ever more sophisticated immune systems. The pathogens’ frequent exposure to other microbes, either in their host or in the environment, provides opportunities for the acquisition or interchange of mobile genetic elements. These DNA elements accessorise the core genome and can play major roles in shaping genome structure and altering the complement of virulence factors. Here, we review the different mobile genetic elements focusing on the more recent discoveries and highlighting their role in shaping bacterial pathogen evolution

Finite Temperature Models of Bose-Einstein Condensation

The theoretical description of trapped weakly-interacting Bose-Einstein condensates is characterized by a large number of seemingly very different approaches which have been developed over the course of time by researchers with very distinct backgrounds. Newcomers to this field, experimentalists and young researchers all face a considerable challenge in navigating through the `maze' of abundant theoretical models, and simple correspondences between existing approaches are not always very transparent. This Tutorial provides a generic introduction to such theories, in an attempt to single out common features and deficiencies of certain `classes of approaches' identified by their physical content, rather than their particular mathematical implementation. This Tutorial is structured in a manner accessible to a non-specialist with a good working knowledge of quantum mechanics. Although some familiarity with concepts of quantum field theory would be an advantage, key notions such as the occupation number representation of second quantization are nonetheless briefly reviewed. Following a general introduction, the complexity of models is gradually built up, starting from the basic zero-temperature formalism of the Gross-Pitaevskii equation. This structure enables readers to probe different levels of theoretical developments (mean-field, number-conserving and stochastic) according to their particular needs. In addition to its `training element', we hope that this Tutorial will prove useful to active researchers in this field, both in terms of the correspondences made between different theoretical models, and as a source of reference for existing and developing finite-temperature theoretical models.Comment: Detailed Review Article on finite temperature theoretical techniques for studying weakly-interacting atomic Bose-Einstein condensates written at an elementary level suitable for non-experts in this area (e.g. starting PhD students). Now includes table of content

Challenges in accessing financial capital as a barrier to immigrant entrepreneurship:evidence from Finland, Kajaani region

Previous research on the topic of immigrant entrepreneurship has found that one of the most important challenges immigrant entrepreneurs are facing is access to financial capital. Empirical evidence of prior scientific research has shown that immigrant entrepreneurs are facing array of challenges including discrimination when accessing financial capital. Motivated by the prior scientific research on the topic, aim of this study is to understand what challenges and restrictions Finnish immigrant entrepreneurs are facing in Kajaani region when accessing financial capital to finance their businesses. Aim of this study is also to explore whether they are utilizing already available financial capital and services offered by government organizations and financial institutions. This study was done with the help of qualitative research methods. Semi-structured interviews were conducted with 5 immigrant entrepreneurs and 1 government official from TE Services from Kajaani region. Findings show that immigrant entrepreneurs in Kajaani region are facing the same challenges as native entrepreneurs, with several important distinctions. First, language barriers, financial literacy, miscommunication, lack of communication and understanding between immigrant entrepreneurs and government and financial institutions represent major challenge when accessing financial capital from both government and financial institutions. Second, difficulties in proving financial responsibility, lack of credit history, lack of long-term bank-customer relationship and collateral are also found to be additional challenges when obtaining financial capital. No evidence on discrimination was found, but there were pointers toward trust issues between immigrant entrepreneurs and financial institutions and government organizations. Because of challenges immigrant entrepreneurs are facing when accessing financial capital, they follow certain patterns when it comes to overcoming financing gaps. As a source of financial capital they are using their own savings, followed by finances obtained from their friends and family, partners and fellow entrepreneurs. Findings show that more often than not, immigrant entrepreneurs are not utilizing available resources, which could potentially affect future of their businesses in a negative way. However, because of limited time and resources available for this master thesis, sample size and type of data available represent the limitation of this study. Hence, this study could serve as a call for a nationwide quantitative study of the topic

New recipe for targeting resistance

The rapid spread of antibiotic-resistant bacteria demands novel treatment approaches that delay or even reverse the evolution of resistance. A new screening strategy identifies two compounds that select against a common tetracycline-resistance gene in Escherichia coli

An SEM study of the haptoral sclerites of the genus Gyrodactylus Nordmann, 1832 (Monogenea) following extraction by digestion and sonication techniques

Techniques for the preparation of haptoral sclerites of Gyrodactylus species for scanning electron microscopy are described. Enzymatic digestion using pepsin allows fresh, frozen and alcohol-fixed material to be examined, but some sclerites, such as the dorsal and ventral bars, are lost. Sonication of fresh and frozen material retained these accessory bars, including the ventral bar membrane, the guard or sickle filament loop on the marginal hooks and even on some occasions ligaments associated with the sclerites. The sclerites of Gyrodactylus spp. from Gasterosteus aculeatus (L.) (three-spined stickleback), Oncorhynchus mykiss (Walbaum) (rainbow trout) and Salvelinus alpinus (L.) (charr) are described from SEM observations following the use of these preparation techniques, and the articulation between the hamuli and bars is commented upon