Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    The species-specific mode of action of the antimicrobial peptide subtilosin against Listeria monocytogenes Scott A
    Kuijk, S.J.A. van; Noll, K.S. ; Chikindas, M.L. - \ 2012
    Letters in Applied Microbiology 54 (2012)1. - ISSN 0266-8254 - p. 52 - 58.
    bacillus-subtilis - bacteriocins - antibiotics - mechanism - pathogen - growth - acid - ph
    Aims: To elucidate the molecular mechanism of action of the antimicrobial peptide subtilosin against the foodborne pathogen Listeria monocytogenes Scott A. Methods and Results: Subtilosin was purified from a culture of Bacillus amylliquefaciens. The minimal inhibitory concentration of subtilosin against L. moilocytogenes Scott A was determined by broth microdilution method. The effect of subtilosin on the transmembrane electrical potential (Ali) and pH gradient (ApH), and its ability to induce efflux of intracellular ATP, was investigated. Subtilosin fully inhibited L. monocytogencs growth at a concentration of 19 fig Subtilosin caused a partial depletion of the AT and had a similar minor effect on the ApIL There was no significant efflux of intracellular ATP. Conclusion: Subtilosin likely acts upon L. monocytogencs Scott A by perturbing the lipid bilayer of the cellular membrane and causing intracellular damage, leading to eventual cell death. Subtilosin's mode of action against L. monocytogcues Scott A differs from the one previously described for another human path()gen, Cam dnerella vaginalis. Significance and Impact of the Study: This is the first report on the specific mode of action of subtilosin against L. monocytogenes and the first report of a bacteriocin with a species specific mode of action
    Antagonistic interactions peak at intermediate genetic similarity
    Schoustra, S.E. ; Dench, J. ; Dali, R. ; Aaron, S.D. ; Kassen, R.K. - \ 2012
    BMC Microbiology 12 (2012). - ISSN 1471-2180
    cystic-fibrosis patients - staphylococcus-aureus - bacteriocins - evolution - spite - virulence - sequence - ecology - pyocins - pao1
    Background Bacteria excrete costly toxins to defend their ecological niche. The evolution of such antagonistic interactions between individuals is expected to depend on both the social environment and the strength of resource competition. Antagonism is expected to be weak among highly similar genotypes because most individuals are immune to antagonistic agents and among dissimilar genotypes because these are unlikely to be competing for the same resources and antagonism should not yield much benefit. The strength of antagonism is therefore expected to peak at intermediate genetic distance. Results We studied the ability of laboratory strains of Pseudomonas aeruginosa to prevent growth of 55 different clinical P. aeruginosa isolates derived from cystic fibrosis patients. Genetic distance was determined using genetic fingerprints. We found that the strength of antagonism was maximal among genotypes of intermediate genetic distance and we show that genetic distance and resource use are linked. Conclusions Our results suggest that the importance of social interactions like antagonism may be modulated by the strength of resource competition
    Soya bean tempe extracts show antibacterial activity against Bacillus cereus cells and spores
    Roubos-van den Hil, P.J. ; Dalmas, E. ; Nout, M.J.R. ; Abee, T. - \ 2010
    Journal of Applied Microbiology 109 (2010)1. - ISSN 1364-5072 - p. 137 - 145.
    rhizopus-oligosporus - food biopreservation - bacteriocins - peptides
    Aims: Tempe, a Rhizopus ssp.-fermented soya bean food product, was investigated for bacteriostatic and/or bactericidal effects against cells and spores of the food-borne pathogen Bacillus cereus. Methods and results: Tempe extract showed a high antibacterial activity against B. cereus ATCC 14579 based on optical density and viable count measurements. This growth inhibition was manifested by a 4 log CFU ml-1 reduction, within the first 15 min of exposure. Tempe extracts also rapidly inactivated B. cereus spores upon germination. Viability and membrane permeability assessments using fluorescence probes showed rapid inactivation and permeabilization of the cytoplasmic membrane confirming the bactericidal mode of action. Cooked beans and Rhizopus grown on different media did not show antibacterial activity, indicating the unique association of the antibacterial activity with tempe. Subsequent characterization of the antibacterial activity revealed that heat treatment and protease addition nullified the bactericidal effect, indicating the proteinaceous nature of the bioactive compound. Conclusions: During fermentation of soya beans with Rhizopus, compounds are released with extensive antibacterial activity against B. cereus cells and spores. Significance and Impact of Study: The results show the potential of producing natural antibacterial compounds that could be used as ingredients in food preservation and pathogen control
    Effect of dispersal and nutrient availability on the competitive ability of toxin-producing yeast
    Wloch-Salamon, D. ; Gerla, D. ; Hoekstra, R.F. ; Visser, J.A.G.M. de - \ 2008
    Proceedings of the Royal Society. B: Biological Sciences 275 (2008)1634. - ISSN 0962-8452 - p. 535 - 541.
    saccharomyces-cerevisiae genome - viral killer toxins - interference competition - promotes biodiversity - escherichia-coli - ecological role - bacteriocins - populations - evolution - microorganisms
    The ecological role of interference competition through toxin production is not well understood. In particular, it is unclear under what conditions the benefits of toxic killing outweigh the metabolic costs involved. A killer advantage has been suggested to rely on local competitive interactions where the benefits of killing accrue to the toxin producer preferentially, but this notion has little empirical support. In addition, contrasting predictions exist about the effect of resource abundance on the benefits of toxin production; this benefit should either be highest when resources are abundant and metabolic costs are relatively low or when resources are scarce and toxic killing is a `last resort strategy¿ to obtain nutrients. Here, we test these predictions for one aspect of competitive ability, that is, the ability of toxin producers to invade a population of sensitive non-producers from a low initial frequency. We use competition experiments between isogenic K1 toxin-producing and non-producing strains of Saccharomyces cerevisiae, where we manipulate dispersal under two extreme nutrient conditions: one environment with and the other without replenishment of nutrients. We find that toxin production is beneficial when dispersal is limited under both nutrient conditions, but only when resources are abundant these outweigh its cost and allow invasion of the producer
    Reducing fitness costs associated with antibiotic resistance: experimental evolution in the filamentous fungus Aspergillus nidulans
    Schoustra, S.E. - \ 2004
    Wageningen University. Promotor(en): Rolf Hoekstra, co-promotor(en): Fons Debets. - Wageningen : S.n. - ISBN 9789085041061 - 142
    emericella nidulans - fungicidentolerantie - antibiotica - geneesmiddelresistentie - lysogenie - bacteriocinen - evolutie - genetica - emericella nidulans - fungicide tolerance - antibiotics - drug resistance - lysogeny - bacteriocins - evolution - genetics
    The 1990s saw the growth of two distinct strands of debates on the transformations and emerging problems besetting the urban space. One of these has focused on the relationship between globalisation and the similar changes metropolitan cities are undergoing, as they become home to numerous global economic agents such as multinational firms. According to it, globalisation can be understood as a worldwide reaching 'space of flows' - of money, information, and physical streams - emerging within a 'network society', and landing into the urban space triggering multiple cultural, political, economic, societal, and spatial transformations. In so doing, globalisation is prompting new challenges in dealing with urban management issues, once the 'space of flows' meets the 'space of place', that is, the physical contiguity of the urban node, govemed by the particularities of the city's regime, such as its political, cultural, and economic background.

    Developing in parallel, the other strand of debates has focused on the relationship between the natural and built environments, exploring the ecological footprint of buildings, their impacts on local infrastructures and new technologies that are emerging to curb them. Rather technocratic, this lint: ofthought describes buildings as one of the main environmental disrupters of modernity - accountable for elevated indexes of energy, water, and finite natural resources' use, and related ecological problems spanning from local infrastructure overburden, to global warming, ozone depletion, deforestation, desertification, and so on.

    Both strands of debates have been elucidating. On the other hand, they have also been incomplete. While demonstrating how globalisation has become a dominating key point for understanding contemporary urban change, the first line overlooks the urban environmental dimension, that is, how globalisation may trigger urban environmental challenges and/or may be a vehicle for introducing environmental management solutions. The other approach, while quantifying the environmental impacts of buildings in general and describing technical solutions to mitigate them, falls short when analysing the societal processes that are leading to, or hindering, an ecological upgrading of buildings - i.e., how such technological modernisation is or may be steered amid different social actors.

    This study aims at making a bridge between such two research lines by providing an environmental perspective to the global city research as well as a societal dimension to the sustainable building literature. As segments of the urban space have transnationalised with globalisation, with the presence of multinational firms and other global economic agents connecting key cities throughout the planet, the skyscraper has turned into a 'transnational building' . This is a local structure that not only rules the skyline of the global city, posing numerous local environmental burdens, but which is now also embedded in the global space of flows, subject to its regimes. This study analyses how the transnational building may become a sustainable building, canalising environmental innovations from the global space of flows into the urban space. By focusing on offices held by multinational firms in specific locations, it explores how and why such firms are - or are not promoting in-house environmental management practices, and whether they may form a worldwide virtuous circle leading to a global network of urban environmental change. Its aim is to understand how sustainable building practices are being activated .in certain urban nodes of the network society and may transcend to other urban nodes, and how the dynamics of urban environmental change at the interface between the space of flows (the environmental regimes of global companies) and the space of places (urban environmental and utility management policies) may vary in view of the different economic and political backgrounds of each city. How is the greening of transnational buildings developing in different urban settings? Which actors are pushing for, and which are hindering, such greening process?

    To deal with these questions, both theoretical perspectives as well as empirical research methods are used. Theory-wise, a central proposition organising the enquiry suggests that a new trend in environmental polities has emerged, in which the state 'retreats' from developing top-down environmental policies while marketfactors start to play a central role in triggering environmental change. While the state remains imperative as an environmental change 'enabler', the dynamics of environmental change is nevertheless implemented by market actors, following an ecological modernisation logic, in which the environment becomes a central criterion in production and consumption processes. Deriving from this, and in the tradition ecological modernisation studies, a central hypothesis this research puts forward is that, in the era of globalisation g/oba/ market actors may trigger urban environmental reforms, with multinational firms concentrating head offices in key cities while dispersing their activities throughout the planet. In this case, such firms may form a virtuous - as well as virtua/ - circle of worldwide urban environmental change.

    To empirically analyse the adequacy of this hypothesis, the study adopts a qualitative and explorative research methodology. This consists of a case study research design, exploring how and why environmental innovations are being triggered in transnational buildings at the interface between local and global societal dynamics in different urban settings. To this end, the in-house environmental management practices of four high environmental-profile multinational companies (ING, Andersen, ABN AMRO, and ffiM) are evaluated in three global cities, which altogether portray a sample of three different 'stateeconomy' combinations: Amsterdam (a democratic, partially state-regulated city with a well-developed environmental capacity), Sao Paulo (a democratic and free market economy context), and Beijing (a state-regulated urban setting). The combination of these three cities and four companies result in 12 case studies of global-local interception, which are investigated making use of personal interviews (in each company in the three cities as weIl as at city planning agencies), in addition to general observations and secondary literature.

    The findings of this research make it clear that, although showing differences, the greening of transnational buildings in the three global cities displays some similarities in certain aspects. First it can be noted that local public actors play a crucial role in activating the environmental reform of transnational buildings. Environmental policies deployed by urban environmental agencies, for instance, may actively trigger or seek to further policies of global companies, resulting in sustainable building practices. In addition, local public actors may develop environmental strategies through legal and economic instruments to attract transnational actors to invest in their local nodes, laying a kind of 'green carpet' for global companies, which would favour certain nodes of the network society for their good environmental performance.

    Secondly, local public actors developing sustainable building policies in cooperation with a multinational company tend to get environmental innovations started also at the level of the 'space of flows', that is, at the level of global company strategies. However, the expectation to see these policies materialise in other urban nodes of the network society does not always turn out to be realistic, resulting too often in weaker corporate environmental policies as compared to original regimes striven in nodes working in citycompany cooperation.

    Third, the research observes that successful cases of global in-house corporate environmental management require companies to 'learn' how to deal with the interaction between the space of flows and the space of place. These companies may pursue a global environmental policy, which, while determining its own standards of in-house environmental performance, always follows the strictest regime in place, whether originated from public policies or from the company's environmental policy. In so doing, such companies are making their sustainable building goals work at all nodes of the network society, regardless the lack of incentives from local agencies. Such approach may not only trespass or by-pass local environmental policies and standards by implementing company strategies more or less autonomously. In some cases it may also activate environmental policies of urban agencies, to be applied in other buildings in the same city. Based on the observations above, this study demonstrates how the realms of urban environmental management and corporate environmental management are not conflicting, as both cities and companies seek to optimise the use of finite resources such as energy and water and ensure sustainability. However a contradiction to be noted regards the shortterm increase in capital expenditure due to the investments sustainable buil ding involves, which goes against the profit component of the corporate management discourse. This research makes it clear that the institutionalisation of sustainable building practices in corporate premises has to a certain extent to be activated by urban policies. In that sense, although examples of market actors prompting environmental change are numerous, the role of public authorities remains crucial in activating the greening of transnational buildings, regardless the different (political-economic) urban settings.

    On the other hand, this research also demonstrates that, beyond multinationals, global market actors as developers and manufacturers are turning into prime agents of this ecological modernisation process, forming a bridge from locality to locality in the transcending of environmental change: distributing new solutions of environmental management, new technologies, new approaches of urban policies, and so. forth. It thereby supports the statement that global market actors are one if not the main engine for launching environmental innovations in transnational urban spaces. In this light, the global virtuous circle of urban environmental reform seems to have been triggered. Yet, to be thoroughly efficient, such virtuous circ1e needs to be ignited by adequate public policies, to be elaborated in accordance with the specificity of each space of place.

    Nisine geholpen met hordentechnologie
    Jong, L.S. de - \ 2001
    Voedingsmiddelentechnologie 34 (2001)8. - ISSN 0042-7934 - p. 49 - 49.
    bacteriocinen - nisine - conserveerkwaliteit - voedselserveermethoden - pathogenen - synergie - combinatie - voedselonderzoek - bacteriocins - nisin - canning quality - food serving methods - pathogens - synergism - combination - food research
    Een combinatie van nisine met carvacrol, thymol of carvon leidde tot een synergistische reductie van het aantal levensvatbare cellen van Listeria monocytogenes en Bacillus cereus. Verslag van een promotieonderzoek
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