196 research outputs found

    Acquired Type III Secretion System Determines Environmental Fitness of Epidemic Vibrio parahaemolyticus in the Interaction with Bacterivorous Protists

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    Genome analyses of marine microbial communities have revealed the widespread occurrence of genomic islands (GIs), many of which encode for protein secretion machineries described in the context of bacteria-eukaryote interactions. Yet experimental support for the specific roles of such GIs in aquatic community interactions remains scarce. Here, we test for the contribution of type III secretion systems (T3SS) to the environmental fitness of epidemic Vibrio parahaemolyticus. Comparisons of V. parahaemolyticus wild types and T3SS-defective mutants demonstrate that the T3SS encoded on genome island VPaI-7 (T3SS-2) promotes survival of V. parahaemolyticus in the interaction with diverse protist taxa. Enhanced persistence was found to be due to T3SS-2 mediated cytotoxicity and facultative parasitism of V. parahaemolyticus on coexisting protists. Growth in the presence of bacterivorous protists and the T3SS-2 genotype showed a strong correlation across environmental and clinical isolates of V. parahaemolyticus. Short-term microcosm experiments provide evidence that protistan hosts facilitate the invasion of T3SS-2 positive V. parahaemolyticus into a coastal plankton community, and that water temperature and productivity further promote enhanced survival of T3SS-2 positive V. parahaemolyticus. This study is the first to describe the fitness advantage of GI-encoded functions in a microbial food web, which may provide a mechanistic explanation for the global spread and the seasonal dynamics of V. parahaemolyticus pathotypes, including the pandemic serotype cluster O3:K6, in aquatic environments

    Protective behaviour of citizens to transport accidents involving hazardous materials: A discrete choice experiment applied to populated areas nearby waterways

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    Background To improve the information for and preparation of citizens at risk to hazardous material transport accidents, a first important step is to determine how different characteristics of hazardous material transport accidents will influence citizens' protective behaviour. However, quantitative studies investigating citizens' protective behaviour in case of hazardous material transport accidents are scarce. Methods A discrete choice experiment was conducted among subjects (19-64 years) living in the direct vicinity of a large waterway. Scenarios were described by three transport accident characteristics: odour perception, smoke/vapour perception, and the proportion of people in the environment that were leaving at their own discretion. Subjects were asked to consider each scenario as realistic and to choose the alternative that was most appealing to them: staying, seekin

    Identification of Motifs of <em>Burkholderia pseudomallei</em>  BimA Required for Intracellular Motility, Actin Binding, and Actin Polymerization

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    Actin-based motility of the melioidosis pathogen Burkholderia pseudomallei requires BimA (Burkholderia intracellular motility A). The mechanism by which BimA mediates actin assembly at the bacterial pole is ill-defined. Toward an understanding of the regions of B. pseudomallei BimA required for intracellular motility and the binding and polymerization of actin, we constructed plasmid-borne bimA variants and glutathione-S-transferase fusion proteins with in-frame deletions of specific motifs. A 13-amino-acid direct repeat and IP(7) proline-rich motif were dispensable for actin binding and assembly in vitro, and expression of the mutated proteins in a B. pseudomallei bimA mutant restored actin-based motility in J774.2 murine macrophage-like cells. However, two WASP homology 2 (WH2) domains were found to be required for actin binding, actin assembly, and plaque formation. A tract of five PDASX direct repeats influenced the polymerization of pyrene-actin monomers in vitro and was required for actin-based motility and intercellular spread, but not actin binding. None of the mutations impaired surface expression or polar targeting of BimA. The number of PDASX repeats varied in natural isolates from two to seven. Such repeats acted additively to promote pyrene-actin polymerization in vitro, with stepwise increases in the rate of polymerization as the number of repeats was increased. No differences in the efficiency of actin tail formation could be discerned between strains expressing BimA variants with two, five, or seven PDASX repeats. The data provide valuable new insights into the role of conserved and variable motifs of BimA in actin-based motility and intercellular spread of B. pseudomallei

    Nature-Based Tourism and Neoliberalism: Concealing Contradictions

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    This paper demonstrates how tourism, including nature based tourism, simultaneously produces and conceals the contradictions of capitalism; this is because it relies on creating attractions, or new sources of accumulation from the very crises it produces. Nature-based tourism is promoted as a ‘win-win’ that can resolve the contradiction between continual economic growth and finite natural resources (Fletcher, 2011; O’Connor, 1988). This is made possible via a process of neoliberalising nature, which cuts the threads that bind ecosystems together, so that the constituent parts can be transformed into new commodities (Büscher et al, 2012; Castree, 2009; Heynen et al, 2007; McCarthy and Prudham, 2004: 275-277; Peck and Theodore, 2007). To draw out these broad arguments, this paper firstly examines the claims around tourism as ‘Green Economy’ – which proponents claim can produce environmentally sustainable economic growth – a benefit also associated with nature-based tourism. I also show that this can be regarded as simply the latest version of an existing debate rather than offering a new intepretation. This is explored further via a comparative analysis of how tourism neoliberalises nature at the scales of the individual animal (elephant trekking in Thailand) and the landscape (by global networks of NGOs operating in Madagascar). In the case of neoliberalisation of nature at the individual animal scale, the notion of bodily fix is also important. It is not just the elephants that are primed for commodity capture, it is the emotional experience of close interactions with elephants which is commodified (Fletcher, 2014: 185; Fletcher and Neves, 2013). Such changes reshape societal relations with nature, but in uneven and incomplete ways. This is underlined by a discussion of the case of the Durban Vision Initiative in Madagascar – which reveals how neoliberalisation was incomplete as a result of its encounter with local level materialities
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