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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‘When breaking you make your soul dance’ Utopian aspirations and subjective transformation in breakdance
Bode Bakker, Maritza ; Nuijten, Monique - \ 2018
African Identities 25 (2018)2. - ISSN 1070-289X - p. 210 - 227.
body - Breakdance - culture - resistance - utopia - youth
This article is based on a study of the Naturalz crew, a ‘breaking’ or breakdancing group in Quito, Ecuador. Breaking is commonly analysed as a subculture of resistance. We analyse two–often neglected–dimensions of this resistance: the significance of utopian aspirations and the role of the body in subjective transformation. We argue that participants enact utopian values in breaking, for instance by affirming the value of street life and people from the streets. Furthermore, we see that breaking leads to subjective transformation among its young practitioners and that the body plays a central role in this change of subject position. It is interesting that girls use breaking to rebel against dominant images of ideal womanhood, resulting in changes in gendered subjectivity. Hence, from disempowered, marginalised young people, breakers turn into determined agents with physical strength and emotional resilience.
Varroa Sensitive Hygiene contributes to naturally selected varroa resistance in honey bees
Panziera, Delphine ; Langevelde, Frank van; Blacquière, Tjeerd - \ 2017
Journal of Apicultural Research 56 (2017)5. - ISSN 0021-8839 - p. 635 - 642.
mites - resistance - selection - varroosis - VSH

The parasitic mite Varroa destructor is a serious threat for western honey bee colonies and beekeepers are compelled to control it to keep their colonies healthy. Yet, by controlling varroa no resistance to the parasite can evolve. As a trial, honey bee colonies have been left untreated in isolated locations to allow development of resistance or tolerance to the mite. These colonies developed an ability to live without control measures against varroa, although the traits responsible for this resistance or tolerance are still unclear. Two of these resistant populations have been studied to test the involvement of specific varroa mite targeted hygienic behaviour varroa sensitive hygiene (VSH) in the acquired resistance. Individual mites were manually introduced into just capped brood cells, after which the brood combs were placed in colonies of the two resistant populations and in control colonies in which varroa had always been controlled. We followed the development of the mites, including possible removals. We found that VSH had increased strongly in one of the selections, up to 40% of the infested cells with mites and pupae were removed, but it had decreased in the other selection, compared to the control colonies. Further we could not conclude from our data that VSH only or preferentially targets reproducing mites, leaving non-reproducing mites undisturbed. The different VSH responses between the two selected resistant honey bee populations lead to conclude that more than one mechanism of resistance may evolve in response to the selection pressure by varroa mites.

Exploring the resistance against root parasitic plants in Arabidopsis and tomato
Cheng, Xi - \ 2017
University. Promotor(en): H.J. Bouwmeester, co-promotor(en): Carolien Ruyter-Spira. - Wageningen : Wageningen University - ISBN 9789463437004 - 305
plants - parasitic plants - arabidopsis thaliana - solanum lycopersicum - host parasite relationships - plant growth regulators - resistance - planten - parasitaire planten - gastheer parasiet relaties - plantengroeiregulatoren - weerstand
Root parasitic plant species such as broomrapes (Orobanche and Phelipanche spp.) and witchweeds (Striga spp.) are notorious agricultural weeds. They cause damage to crops by depriving them of water, nutrients and assimilates via a vascular connection. The difficulty in controlling root parasitic weeds is largely due to their intricate lifecycle and partially underground lifestyle. Their life cycle includes processes such as germination of the seed, the formation of the vascular connection with the host, the growth and development of the parasite after attachment and the emergence of shoots and flowers aboveground. The germination of many parasitic plants is induced by strigolactones that were recently shown to also be signalling compounds that stimulate mycorrhizal symbiosis. In addition, in the past few years, their role in plant development and plant defense has been established revealing them as a new class of plant hormones that exert their function likely in interaction with other hormones.
'Alerte plant kan een aanval van schimmels weerstaan' : onderzoek naar invloed rood licht op weerbaarheid
Hofland-Zijlstra, Jantineke - \ 2016
fungi - fungus control - resistance - red light - agricultural research - greenhouse horticulture - plant pests - plants - immune system
RNA ‘Information Warfare’ in Pathogenic and Mutualistic Interactions
Chaloner, Thomas ; Kan, Jan A.L. van; Grant-Downton, Robert T. - \ 2016
Trends in Plant Science 21 (2016)9. - ISSN 1360-1385 - p. 738 - 748.
fungus - infection - non-coding RNA - pathogen - resistance

Regulatory non-coding RNAs are emerging as key players in host–pathogen interactions. Small RNAs such as microRNAs are implicated in regulating plant transcripts involved in immunity and defence. Surprisingly, RNAs with silencing properties can be translocated from plant hosts to various invading pathogens and pests. Small RNAs are now confirmed virulence factors, with the first report of fungal RNAs that travel to host cells and hijack post-transcriptional regulatory machinery to suppress host defence. Here, we argue that trans-organism movement of RNAs represents a common mechanism of control in diverse interactions between plants and other eukaryotes. We suggest that extracellular vesicles are the key to such RNA movement events. Plant pathosystems serve as excellent experimental models to dissect RNA ‘information warfare’ and other RNA-mediated interactions.

On the evolution of azole resistance in Aspergillus fumigatus
Zhang, J. - \ 2016
University. Promotor(en): Bas Zwaan; P.E. Verweij, co-promotor(en): Fons Debets; Sijmen Schoustra. - Wageningen : Wageningen University - ISBN 9789462578555 - 183 p.
aspergillus fumigatus - azoles - triazoles - aspergillosis - resistance - life cycle - asexual reproduction - sexual reproduction - experimental evolution - evolutionary genetics - agriculture - composting - medicine - azolen - triazolen - aspergillose - weerstand - levenscyclus - ongeslachtelijke voortplanting - geslachtelijke voortplanting - experimentele evolutie - evolutionaire genetica - landbouw - compostering - geneeskunde

During the last decade azole resistance has increasingly been reported in Aspergillus fumigatus, which is a fungal pathogen involved in the vast majority of invasive aspergillosis infections in humans, and is now a global public health concern. Antifungal azoles, especially triazoles, are the drugs of choice for medical treatment. However, this treatment is hampered by the emergence of multi-azole resistant A. fumigatus isolates, especially the highly resistant variants TR34/L98H and TR46 /Y121F/T289A. Therefore, to control this disease, it is essential to elucidate by what mechanisms resistance emerges, how resistance spreads and how resistant genotypes persist in environments without azoles. The presented thesis shows the relevance of the life cycle of A. fumigatus to the development of azole resistance and possible evolutionary routes that lead to it. The work highlights the importance of fungal biology and evolution towards understanding the development of azole resistance in fungi. We conclude that azole resistance in A. fumigatus is a consequence of selection pressure by azole in the environment on the genetic variation generated via various aspects in the A. fumigatus life cycle. This thesis also introduces an experimental evolution approach to study the dynamics and mechanisms of the evolution of azole resistance. In addition, we investigate what condition can lead an environment to be a possible hotspot for the development of resistance. Finally, we link this to the potential conditions under which resistance can emerge and spread in the lungs of humans and how this depends on the specific azole used.

Quantitative and ecological aspects of Listeria monocytogenes population heterogeneity
Metselaar, K.I. - \ 2016
University. Promotor(en): Marcel Zwietering; Tjakko Abee, co-promotor(en): Heidy den Besten. - Wageningen : Wageningen University - ISBN 9789462577664 - 173 p.
listeria - listeria monocytogenes - stress - stress tolerance - ribosomes - proteins - lactobacillus plantarum - behaviour - ecological assessment - genome analysis - dna sequencing - resistance - heterogeneity - stresstolerantie - ribosomen - eiwitten - gedrag - ecologische beoordeling - genoomanalyse - dna-sequencing - weerstand - heterogeniteit

Bacterial stress response and heterogeneity therein is one of the biggest challenges posed by minimal processing. Heterogeneity and resulting tailing representing a more resistant fraction of the population, can have several causes and can be transient or stably in nature. Stable increased stress resistance is caused by alterations in the genome and therefore inheritable and is referred to as stable stress resistant variants. Also L. monocytogenes exhibits a heterogeneous response upon stress exposure which can be partially attributed to the presence of stable stress resistant variants. Adverse environments were shown to select for stable stress resistant variants. The objective of the research described in this thesis was to evaluate if L. monocytogenes population diversity and the presence of stable resistant variants is a general phenomenon that is observed upon different types of stress exposure, to get more insight in the mechanisms leading to increased resistance and to evaluate the ecological behaviour and potential impact on food safety of these stable resistant variants. Acid stress was chosen as it is an important hurdle both in food preservation, as well as in stomach survival.

First, the non-linear inactivation kinetics of L. monocytogenes upon acid exposure were quantitatively described. A commonly used biphasic inactivation model was reparameterized, which improved the statistical performance of the model and resulted in more accurate estimation of the resistant fraction within L. monocytogenes WT populations. The observed tailing suggested that stable stress resistant variants might also be found upon acid exposure. Indeed, 23 stable acid resistant variants of L. monocytogenes LO28 were isolated from the tail after exposure of late-exponential phase cells to pH 3.5 for 90 min, with different degrees of acid resistance amongst them. Increased acid resistance showed to be significantly correlated to reduced growth rate. Studying the growth boundaries of the WT and a representative set of variants indicated that the increased resistance of the variants was only related to survival of severe pH stress but did not allow for better growth or survival at mild pH stress.
A set of variants were further characterized phenotypically and cluster analysis was performed. This resulted in three clusters and four individual variants and revealed multiple-stress resistance, with both unique and overlapping features related to stress resistance, growth, motility, biofilm formation and virulence indicators. A higher glutamate decarboxylase (GAD) activity correlated with increased acid resistance. Whole genome sequencing of a set of variants was performed and revealed mutations in rpsU, encoding ribosomal protein S21. This rpsU mutation was found in all 11 variants comprising the largest phenotypic cluster, indicating a potential role of this ribosomal protein in stress resistance. Mutations in ctsR, which were previously shown to be responsible for increased resistance of heat and HHP resistant variants, were not found in the acid resistant variants. This underlined that large population diversity exists within one L. monocytogenes strain and that different adverse conditions drive selection for different variants.

Next, the performance in mixed species biofilms with Lactobacillus plantarum was evaluated, as well as their benzalkonium chloride (BAC) resistance in these biofilms. It was hypothesized that the acid resistant variants might also show better survival in biofilms with L. plantarum, which provide an acidic environment by lactose fermentation with pH values below the growth boundary of L. monocytogenes when biofilms mature. L. monocytogenes LO28 WT and eight acid resistant variants were capable of forming mixed biofilms with L. plantarum at 20°C and 30°C in BHI supplemented with manganese and glucose. Some of the variants were able to withstand the low pH in the mixed biofilms for a longer time than the WT and there were clear differences in survival between the variants which could not be correlated to (lactic) acid resistance alone. Adaptation to mild pH of liquid cultures during growth to stationary phase increased the acid resistance of some variants to a greater extent than of others, which could be correlated to increased survival in the mixed biofilms. There were no clear differences in BAC resistance between the wild type and variants in mixed biofilms.

Lastly, a set of robustness and fitness parameters of WT and variants was obtained and used to model their growth behaviour under combined mild stress conditions and to model their performance in a simulated food chain. This gave more insight in the trade-off between increased stress resistance and growth capacity. Predictions of performance were validated in single and mixed cultures by plate counts and by qPCR in which WT and an rpsU deletion variant were distinguished by specific primers. Growth predictions for WT and rpsU deletion variant were matching the experimental data generally well. Globally, the variants are more robust than the WT but the WT grows faster than most variants. Validation of performance in a simulated food chain consisting of subsequent growth and inactivation steps, confirmed the trend of higher growth fitness and lower stress robustness for the WT compared to the rpsU variant. This quantitative data set provides insights into the conditions which can select for stress resistant variants in industrial settings and their potential persistence in food processing environments.

In conclusion, the work presented in this thesis highlights the population diversity of L. monocytogenes and the impact of environmental conditions on the population composition, which is of great importance for minimal processing. The work of this thesis resulted in more insight in the mechanisms underlying increased resistance of stress resistant variants and quantitative data on the behaviour of stress resistant variants which can be implemented in predictive microbiology and quantitative risk assessments aiming at finding the balance between food safety and food quality.

Territorial pluralism: water users’ multi-scalar struggles against state ordering in Ecuador’s highlands
Hoogesteger, Jaime ; Boelens, Rutgerd ; Baud, Michiel - \ 2016
Water International 41 (2016)1. - ISSN 0250-8060 - p. 91 - 106.
Ecuador - irrigation - resistance - scale - territorial pluralism - water reforms - water user organization
Resistentieveredeling - Verdedigingsmechanisme : Kennisclip Bogo-project e-learning
Hop, M.E.C.M. - \ 2016
Groen Kennisnet
resistance breeding - susceptibility - resistance - tolerance - host pathogen interactions - plant protection - teaching materials - disease resistance - resistentieveredeling - vatbaarheid - weerstand - tolerantie - gastheer-pathogeen interacties - gewasbescherming - lesmaterialen - ziekteresistentie
Deze kennisclip maakt onderdeel uit van de lesmodule Resistentie Veredeling van het CIV T&U.
Micropolitics in Resistance: The Micropolitics of Large-Scale Natural Resource Extraction in South East Asia
Rasch, E.D. ; Kohne, F.M. - \ 2016
Society & Natural Resources 29 (2016)4. - ISSN 0894-1920 - p. 479 - 492.
Micropolitics - resistance - natural resources - extraction - south east asia - society
This article analyzes Southeast Asian local communities’ resistance against the globalizing large-scale exploitation of natural resources using a micropolitical ecology approach. It focuses on how communities struggle for livelihoods, both resisting and appropriating globalized practices and narratives. Our ethnographic material encompasses natural resource conflicts in two communities: one on Sumatra (Indonesia) and one on Palawan (the Philippines). In both communities foreign and national companies have laid claims on community lands, transforming local power relations and wealth distribution as well as the relations of the communities vis-à-vis globalized production and the state. Communities often split over such transformations; some members negotiate a share in the globalized markets, while others organize resistance against these developments. The article argues that the specifics of this resistance against globalization can only be explained by taking into account the “micropolitics” within which they are produced, which calls for an ethnographic research approach to globalization.
Emergent strategies for detection and control of biofilms in food processing environments
Besten, H.M.W. den; Ding, Y. ; Abee, T. ; Liang, Yang - \ 2016
In: Advances in Food Biotechnology / Rai V, Ravishankar, Chichester, UK : John Wiley and Sons - ISBN 9781118864555
biofilm - resistance - detection - control - dispersal
Biofilms are dense surface-attached microbial communities consisting of bacterial colonies embedded in their self-generated matrix materials. Different bacteria species that exist within a biofilm are positioned within many different microenvironments defined by nutrient availability, pH and oxygen levels. To adapt to these myriad niches, bacteria therefore show numerous phenotypes and enormous metabolic and replicative heterogeneity. This heterogeneity provides the biofilm community with great capacity to withstand challenges. Biofilms formed in the food-processing environments cause recalcitrant contaminations and food spoilage, which pose a huge threat to public health. The distinct physiology and slow growth rate of biofilm cells hinder the detection of biofilms hidden in the food-processing environments. Conventional cleaning and disinfecting strategies could be ineffective to eradicate biofilms. The present chapter will focus on describing the latest strategies for detection and control of biofilms in food-processing environments.
Resistance identification and rational process design in Capacitive Deionization
Dykstra, Jouke ; Zhao, R. ; Biesheuvel, P.M. ; Wal, A. van der - \ 2016
Water Research 88 (2016). - ISSN 0043-1354 - p. 358 - 370.
ionentransport - weerstand - waterzuivering - ontzilting - elektrodes - ionenuitwisseling - specifieke ionenelektrodes - ion transport - resistance - water treatment - desalination - electrodes - ion exchange - specific ion electrodes
Capacitive Deionization (CDI) is an electrochemical method for water desalination employing porous carbon electrodes. To enhance the performance of CDI, identification of electronic and ionic resistances in the CDI cell is important. In this work, we outline a method to identify these resistances. We illustrate our method by calculating the resistances in a CDI cell with membranes (MCDI) and by using this knowledge to improve the cell design. To identify the resistances, we derive a full-scale MCDI model. This model is validated against experimental data and used to calculate the ionic resistances across the MCDI cell. We present a novel way to measure the electronic resistances in a CDI cell, as well as the spacer channel thickness and porosity after assembly of the MCDI cell. We identify that for inflow salt concentrations of 20 mM the resistance is mainly located in the spacer channel and the external electrical circuit, not in the electrodes. Based on these findings, we show that the carbon electrode thickness can be increased without significantly increasing the energy consumption per mol salt removed, which has the advantage that the desalination time can be lengthened significantly.
Invasieve soorten Waddenzee: : Ecosysteem resistentie en de Filipijnse tapijtschelp
Sneekes, A.C. ; Mendez Merino, Natalia ; Weide, B.E. van der; Glorius, S.T. ; Tamis, J.E. - \ 2015
Den Helder : IMARES (Rapport / IMARES C175/15) - 67 p.
invasieve soorten - schaaldieren - veevervoer - weerstand - aquatische ecosystemen - milieueffect - waddenzee - nederland - invasive species - shellfish - transport of animals - resistance - aquatic ecosystems - environmental impact - wadden sea - netherlands
Genomics spurs rapid advances in our understanding of the biology of vascular wilt pathogens in the genus Verticillium
Klimes, A. ; Dobinson, K.F. ; Thomma, B. ; Klosterman, S.J. - \ 2015
Annual Review of Phytopathology 53 (2015). - ISSN 0066-4286 - p. 181 - 198.
protein-kinase gene - molecular characterization - functional-analysis - microsclerotia development - ethylene perception - hydrophobin gene - dahliae kleb - tomato ve1 - resistance - expression
The availability of genomic sequences of several Verticillium species triggered an explosion of genome-scale investigations of mechanisms fundamental to the Verticillium life cycle and disease process. Comparative genomics studies have revealed evolutionary mechanisms, such as hybridization and interchromosomal rearrangements, that have shaped these genomes. Functional analyses of a diverse group of genes encoding virulence factors indicate that successful host xylem colonization relies on specific Verticillium responses to various stresses, including nutrient deficiency and host defense–derived oxidative stress. Regulatory pathways that control responses to changes in nutrient availability also appear to positively control resting structure development. Conversely, resting structure development seems to be repressed by pathways, such as those involving effector secretion, which promote responses to host defenses. The genomics-enabled functional characterization of responses to the challenges presented by the xylem environment, accompanied by identification of novel virulence factors, has rapidly expanded our understanding of niche adaptation in Verticillium species.
Mating type and sexual fruiting body of Botrytis elliptica, the causal agent of fire blight in lily
Terhem, R.B. ; Staats, M. ; Kan, J.A.L. van - \ 2015
European Journal of Plant Pathology 142 (2015)3. - ISSN 0929-1873 - p. 615 - 624.
cinerea - leaves - resistance - infection - behavior - system
Botrytis elliptica is a necrotrophic pathogen that specifically infects Lilium species. Previous records show that B. elliptica collected in the field can successfully develop apothecia in vitro, however, there are no formal descriptions of apothecia of B. elliptica. The aim of this study was to analyse the sequence of the mating type loci of B. elliptica and produce apothecia in the laboratory in order to describe their morphology. The sequences of both MAT alleles (MAT1-1 or MAT1-2) of B. elliptica were determined and compared to the sister taxa, Botrytis cinerea and Sclerotinia sclerotiorum. Two strains of each mating type were used in crosses under controlled conditions to produce apothecia. Primordium rupture from sclerotial tissue occurred 74 days after fertilization and a mature apothecium formed within 1 month after rupture. The apothecia are 7 to 12 mm in height with a disk of 3 to 4 mm in diameter and 0.5 to 1 mm in thickness. The apothecial disk is usually umbilicate, depressed to funnel and rounded in shape. The number of apothecia growing on a sclerotium was one to nine. Asci are long, cylindrical with a size of 208¿×¿14 µm, thin walled and bearing eight ascospores. Ascospores are hyaline in colour, ellipsoidal with rounded ends, usually 18 to 24 µm in length and 6 to 10 µm in width (mean 19.5¿×¿8 µm). Ascospores were infectious on lily leaves.
The diversion of 2-C-methyl-D-erythritol-2,4-cyclodiphosphate from the 2-C-methyl-D-erythritol 4-phosphate pathway to hemiterpene glycosides mediates stress responses in Arabidopsis thaliana
Gonzalez-Cabanelas, D. ; Wright, L.P. ; Paetz, C. ; Onkokesung, N. ; Gershenzon, J. ; Rodriguez-Concepcion, M. ; Phillips, M.A. - \ 2015
The Plant Journal 82 (2015)1. - ISSN 0960-7412 - p. 122 - 137.
plant defensin gene - isoprenoid biosynthesis - salicylic-acid - gas-chromatography - mass-spectrometry - mep pathway - synthase - resistance - jasmonate - reveals
2-C-Methyl-D-erythritol-2,4-cyclodiphosphate (MEcDP) is an intermediate of the plastid-localized 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway which supplies isoprenoid precursors for photosynthetic pigments, redox co-factor side chains, plant volatiles, and phytohormones. The Arabidopsis hds-3 mutant, defective in the 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate synthase step of the MEP pathway, accumulates its substrate MEcDP as well as the free tetraol 2-C-methyl-D-erythritol (ME) and glucosylated ME metabolites, a metabolic diversion also occurring in wild type plants. MEcDP dephosphorylation to the free tetraol precedes glucosylation, a process which likely takes place in the cytosol. Other MEP pathway intermediates were not affected in hds-3. Isotopic labeling, dark treatment, and inhibitor studies indicate that a second pool of MEcDP metabolically isolated from the main pathway is the source of a signal which activates salicylic acid induced defense responses before its conversion to hemiterpene glycosides. The hds-3 mutant also showed enhanced resistance to the phloem-feeding aphid Brevicoryne brassicae due to its constitutively activated defense response. However, this MEcDP-mediated defense response is developmentally dependent and is repressed in emerging seedlings. MEcDP and ME exogenously applied to adult leaves mimics many of the gene induction effects seen in the hds-3 mutant. In conclusion, we have identified a metabolic shunt from the central MEP pathway that diverts MEcDP to hemiterpene glycosides via ME, a process linked to balancing plant responses to biotic stress.
Influence of food matrix on outgrowth heterogeneity of heat damaged Bacillus cereus spores
Warda, A.K. ; Besten, H.M.W. den; Sha, N. ; Abee, T. ; Nierop Groot, M.N. - \ 2015
International Journal of Food Microbiology 201 (2015). - ISSN 0168-1605 - p. 27 - 34.
cooked chilled foods - incubation-temperature - recovery medium - population heterogeneity - clostridium-perfringens - individual spores - subtilis spores - germination - resistance - atcc-14579
Spoilage of heat treated foods can be caused by the presence of surviving spore-formers. It is virtually impossible to prevent contamination at the primary production level as spores are ubiquitous present in the environment and can contaminate raw products. As a result spore inactivation treatments are widely used by food producing industries to reduce the microbial spore loads. However consumers prefer mildly processed products that have less impact on its quality and this trend steers industry towards milder preservation treatments. Such treatments may result in damaged instead of inactivated spores, and these spores may germinate, repair, and grow out, possibly leading to quality and safety issues. The ability to repair and grow out is influenced by the properties of the food matrix. In the current communication we studied the outgrowth from heat damaged Bacillus cereus ATCC 14579 spores on Anopore membrane, which allowed following outgrowth heterogeneity of individual spores on broccoli and rice-based media as well as standard and mildly acidified (pH 5.5) meat-based BHI. Rice, broccoli and BHI pH 5.5 media resulted in delayed outgrowth from untreated spores, and increased heterogeneity compared to BHI pH 7.4, with the most pronounced effect in rice media. Exposure to wet heat for 1 min at 95 °C caused 2 log inactivation and approximately 95% of the spores in the surviving fraction were damaged resulting in substantial delay in outgrowth based on the time required to reach a maximum microcolony size of 256 cells. The delay was most pronounced for heat-treated spores on broccoli medium followed by spores on rice media (both untreated and treated). Interestingly, the increase in outgrowth heterogeneity of heat treated spores on BHI pH 7.4 was more pronounced than on rice, broccoli and BHI pH 5.5 conceivably reflecting that conditions in BHI pH 7.4 better support spore damage repair. This study compares the effects of three main factors, namely heat treatment, pH of BHI and the effect of food matrix highlighting the impact of different (model) food recovery media on outgrowth efficiency and heterogeneity of non-heat-treated and heat-damaged B. cereus spores.
Characterisation of biofilms formed by Lactobacillus plantarum WCFS1 and food spoilage isolates
Fernández Ramírez, M.D. ; Smid, E.J. ; Abee, T. ; Nierop Groot, M.N. - \ 2015
International Journal of Food Microbiology 207 (2015). - ISSN 0168-1605 - p. 23 - 29.
lactic-acid bacteria - enterococcal surface protein - listeria-monocytogenes - pseudomonas-putida - bacillus-subtilis - starter cultures - genetic-analysis - rhamnosus gg - resistance - industry
Lactobacillus plantarum has been associated with food spoilage in a wide range of products and the biofilm growth mode has been implicated as a possible source of contamination. In this study we analysed the biofilm forming capacity of L. plantarum WCFS1 and six food spoilage isolates. Biofilm formation as quantified by crystal violet staining and colony forming units was largely affected by the medium composition, growth temperature and maturation time and by strain specific features. All strains showed highest biofilm formation in Brain Heart Infusion medium supplemented with manganese and glucose. For L. plantarum biofilms the crystal violet (CV) assay, that is routinely used to quantify total biofilm formation, correlates poorly with the number of culturable cells in the biofilm. This can in part be explained by cell death and lysis resulting in CV stainable material, conceivably extracellular DNA (eDNA), contributing to the extracellular matrix. The strain to strain variation may in part be explained by differences in levels of eDNA, likely as result of differences in lysis behaviour. In line with this, biofilms of all strains tested, except for one spoilage isolate, were sensitive to DNase treatment. In addition, biofilms were highly sensitive to treatment with Proteinase K suggesting a role for proteins and/or proteinaceous material in surface colonisation. This study shows the impact of a range of environmental factors and enzyme treatments on biofilm formation capacity for selected L. plantarum isolates associated with food spoilage, and may provide clues for disinfection strategies in food industry.
QTL analysis for stomatal functioning in tetraploid Rosa x hybrida grown at high relative air humidity and its implications on postharvest longevity
Carvalho, D.R.A. ; Koning, C.F.S. ; Fanourakis, D. ; Vasconcelos, M.W. ; Carvalho, S.M.P. ; Heuvelink, E. ; Krens, F.A. ; Maliepaard, C.A. - \ 2015
Molecular Breeding 35 (2015). - ISSN 1380-3743 - 11 p.
marker-assisted selection - water relations - cut roses - in-vitro - traits - environments - conductance - sensitivity - improvement - resistance
High relative air humidity (RH = 85 %) during leaf development disturbs stomatal functioning leading to excessive water loss in conditions of high evaporative demand, resulting in severe reduction in postharvest longevity. In roses, this effect depends on the genotype, opening the possibility for breeding cultivars with more responsive stomata. In this study, we aim at identifying genomic regions associated with the control of water loss following growth at high RH. The F1 generation (108 offspring) and the two parents (P540 and P867) of a tetraploid cut rose population grown at high (85 %) RH were phenotyped for stomatal control to water loss by assessing the relative water content after 4 h of leaflet desiccation (RWC_4 h). The RWC_4 h varied between 7 and 62 % across the 110 studied individuals, with parents P540 and P867 showing 51 and 20 % RWC_4 h, respectively. Based on these data, a quantitative trait locus (QTL) analysis was performed. The impact of the identified QTLs on postharvest longevity of ten selected offspring was further evaluated. Three QTLs were identified: two major [positioned on linkage group 5 of the integrated consensus map (ICM 5) of both parents and on ICM 2 of the parent P867] and one putative minor (mapped to ICM 6 of both parents), explaining 32 % of the variability in the RWC_4 h. Low RWC_4 h was found to be a good proxy for eliminating the offspring with short vase life. This study constitutes a first step toward identifying the most likely regions for genes of interest controlling stomatal functioning in high RH-grown plants.
Early life microbial colonization of the gut and intestinal development differ between genetically divergent broiler lines
Schokker, D. ; Veninga, G. ; Vastenhouw, S.A. ; Bossers, A. ; Bree, F.M. de; Kaal-Lansbergen, L.M.T.E. ; Rebel, J.M.J. ; Smits, M.A. - \ 2015
BMC Genomics 16 (2015). - ISSN 1471-2164
salmonella-enteritidis colonization - innate immune responsiveness - pro-inflammatory cytokine - barrier function - gastrointestinal-tract - epithelial-cells - host genotype - double-blind - chickens - resistance
Host genetic makeup plays a role in early gut microbial colonization and immune programming. Interactions between gut microbiota and host cells of the mucosal layer are of paramount importance for a proper development of host defence mechanisms. For different livestock species, it has already been shown that particular genotypes have increased susceptibilities towards disease causing pathogens. The objective of this study was to investigate the impact of genotypic variation on both early microbial colonization of the gut and functional development of intestinal tissue. From two genetically diverse chicken lines intestinal content samples were taken for microbiota analyses and intestinal tissue samples were extracted for gene expression analyses, both at three subsequent time-points (days 0, 4, and 16).
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