4,287 research outputs found

    Evolution of virulence in opportunistic pathogens: generalism, plasticity, and control

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    Standard virulence evolution theory assumes that virulence factors are maintained because they aid parasitic exploitation, increasing growth within and/or transmission between hosts. An increasing number of studies now demonstrate that many opportunistic pathogens (OPs) do not conform to these assumptions, with virulence factors maintained instead because of advantages in non-parasitic contexts. Here we review virulence evolution theory in the context of OPs and highlight the importance of incorporating environments outside a focal virulence site. We illustrate that virulence selection is constrained by correlations between these external and focal settings and pinpoint drivers of key environmental correlations, with a focus on generalist strategies and phenotypic plasticity. We end with a summary of key theoretical and empirical challenges to be met for a fuller understanding of OPs

    Extending the CRESST-II commissioning run limits to lower masses

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    Motivated by the recent interest in light WIMPs of mass ~O(10 GeV), an extension of the elastic, spin-independent WIMP-nucleon cross-section limits resulting from the CRESST-II commissioning run (2007) are presented. Previously, these data were used to set cross-section limits from 1000 GeV down to ~17 GeV, using tungsten recoils, in 47.9 kg-days of exposure of calcium tungstate. Here, the overlap of the oxygen and calcium bands with the acceptance region of the commissioning run data set is reconstructed using previously published quenching factors. The resulting elastic WIMP cross section limits, accounting for the additional exposure of oxygen and calcium, are presented down to 5 GeV.Comment: 4 pages, 4 figure

    “We Are The Gap: Understanding the Inclusion of Immigrants in Moroccan Left-Wing Politics”

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    This project seeks to understand to what extent immigrants are included in left-wing politics in Morocco. In 2011, King Mohammed VI named Morocco an executive constitutional monarchy. One can argue that this means Morocco is moving in the direction of democracy, but is democracy what left-wing political parties are truly advocating for? And if they are, does the left include marginalized people it advocates for? Particularly, how are immigrants fighting for their own rights in Morocco, and to what extent are Moroccan left-wing political parties centering and uplifting the voices of immigrants, if at all

    Broken Bottles

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    Education Policy and mental weakness:a response to a mental health crisis

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    Educationalists have been concerned with the labelling and treatment of children with mental health difficulties in the education system in England for some time (Timimi 2002; Rose 2005; Jull 2008, Cole 2015). These concerns have centred on the role of policy in ‘othering’ such students as deviant learners. The unprecedented number of children suffering from mental illnesses, has forced policymakers to address children’s mental health difficulties. This has involved the identification of a sub-set of the school population experiencing ‘less-severe’ mental health issues, to be addressed through a suite of policy interventions delivered by whole-school approaches, but targeted towards children situated as mentally ‘weak’. Drawing upon a Foucauldian theory of governmentality that addresses children’s behavioural motivations (Rose 1989; Millar and Rose 1990; Foucault 2001; 2008; Popkewitz 2012) an in-depth analysis of a number of educational policy initiatives related to mental health, is conducted, that it is argued are fundamentally flawed. This analysis is followed by a discussion of the performative culture of High Stakes Testing in contributing to children’s mental health difficulties. Here it is argued that a narrative of mental weakness serves to justify a neoliberal rationality towards the treatment of children for whom the performative logic assumed to motivate all learners, fails

    The coevolution of toxin and antitoxin genes drives the dynamics of bacterial addiction complexes and intragenomic conflict

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    Bacterial genomes commonly contain ‘addiction’ gene complexes that code for both a toxin and a corresponding antitoxin. As long as both genes are expressed, cells carrying the complex can remain healthy. However, loss of the complex (including segregational loss in daughter cells) can entail death of the cell. We develop a theoretical model to explore a number of evolutionary puzzles posed by toxin–antitoxin (TA) population biology. We first extend earlier results demonstrating that TA complexes can spread on plasmids, as an adaptation to plasmid competition in spatially structured environments, and highlight the role of kin selection. We then considered the emergence of TA complexes on plasmids from previously unlinked toxin and antitoxin genes. We find that one of these traits must offer at least initially a direct advantage in some but not all environments encountered by the evolving plasmid population. Finally, our study predicts non-transitive ‘rock-paper-scissors’ dynamics to be a feature of intragenomic conflict mediated by TA complexes. Intragenomic conflict could be sufficient to select deleterious genes on chromosomes and helps to explain the previously perplexing observation that many TA genes are found on bacterial chromosomes

    Synergy and Group Size in Microbial Cooperation

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    Microbes produce many molecules that are important for their growth and development, and the consumption of these secretions by nonproducers has recently become an important paradigm in microbial social evolution. Though the production of these public goods molecules has been studied intensely, little is known of how the benefits accrued and costs incurred depend on the quantity of public good molecules produced. We focus here on the relationship between the shape of the benefit curve and cellular density with a model assuming three types of benefit functions: diminishing, accelerating, and sigmoidal (accelerating then diminishing). We classify the latter two as being synergistic and argue that sigmoidal curves are common in microbial systems. Synergistic benefit curves interact with group sizes to give very different expected evolutionary dynamics. In particular, we show that whether or not and to what extent microbes evolve to produce public goods depends strongly on group size. We show that synergy can create an “evolutionary trap” which can stymie the establishment and maintenance of cooperation. By allowing density dependent regulation of production (quorum sensing), we show how this trap may be avoided. We discuss the implications of our results for experimental design
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