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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    Physiological and molecular adaptations of Lactococcus lactis to near-zero growth conditions
    Ercan, O. - \ 2014
    Wageningen University. Promotor(en): Michiel Kleerebezem, co-promotor(en): Eddy Smid. - Wageningen : Wageningen University - ISBN 9789462570719 - 206
    lactococcus lactis - adaptatiefysiologie - voedselmicrobiologie - groeitempo - groeispanning - transcriptomica - metabolomica - lactococcus lactis - adaptation physiology - food microbiology - growth rate - growth stress - transcriptomics - metabolomics

    Lactococcus lactis is an important lactic acid bacteria (LAB) species that is used for the manufacture of dairy products, such as cheese, buttermilk, and other fermented products. The predominant function of this bacterium in dairy fermentation is the production of lactic acid, as its major fermentation end-product that contributes to preservation and microbial safety of the product. Moreover, L. lactis is frequently encountered in natural ecosystems such as in (rotting) plant material.

    Due to restricted energy source availability, natural microbial communities commonly live in a situation that can be characterized as ‘hunger’, which is different from strict nutrient-starvation. As a consequence, environmental microbes commonly grow at very low-growth rates as compared to laboratory cultures. Analogously, microorganisms can experience such nutrient-poor conditions in diverse industrial fermentation applications. For example, LAB encounter extreme low or no energy source availability during the extended ripening process of cheeses or dry sausages, which can take months. Despite these harsh environmental conditions, many LAB are able to remain viable in these processes for months and sustain a low-level metabolic activity, which plays an important role in their contribution to flavor and aroma formation in the product matrix.

    In this thesis, the quantitative physiology of L. lactis at near-zero specific growth rates was studies, employing both metabolic and genome-wide transcriptome studies in an experimental set-up of carbon-limited retentostat cultivation. Chapter 2 describes how retentostat cultivation enables uncoupling of growth and non-growth related processes in L. lactis, allowing the quantitative analysis of the physiological adaptations of this bacterium to near-zero growth rates. In chapter 3, transcriptome and metabolome analyses were integrated to understand the molecular adaptation of L. lactis to near-zero specific growth rate, and expand the studies in chapter 2 towards gene regulations patterns that play a profound role in zero-growth adaptation. Chapter 4 describes the enhanced robustness to several stress conditions of L. lactis after its adaptation to extremely low-specific growth rate by carbon-limited retentostat cultivation. In this chapter correlations were modelled that quantitatively and accurately describe the relationships between growth-rate, stress-robustness, and stress-gene expression levels, revealing correlation coefficients for each of the varieties involved. Chapter 5 evaluates the distinction between the transcriptome responses to extended carbon-limited growth and severe starvation conditions, where the latter condition was elicited by switching off the medium supply of the retentostat cultures described in chapter 1. Chapter 6 highlights the comparison of the physiological and molecular adaptations of industrially important microorganisms towards carbon-limited retentostat conditions. In conclusion, this thesis describes the quantitative physiological, metabolic, and genome-wide transcriptional adaptations of L. lactis at near-zero specific growth rates induced by carbon source limited retentostat cultivation, and compares these molecular adaptations to those elicited by strict carbon-starvation conditions.

    Mogelijkheden om vroeg tijdig bladrandproblemen te signaleren met MIPS bij Hortensia
    Noort, F.R. van; Jalink, H. - \ 2010
    Bleiswijk : Wageningen UR Glastuinbouw (Rapport / GTB 1027) - 14
    gewasbescherming - groeispanning - hydrangea - afwijkingen, planten - potplanten - bladeren - bladvlekkenziekte - fluorescerend licht - meting - plant protection - growth stress - plant disorders - pot plants - leaves - leaf spotting - fluorescent light - measurement
    Met geavanceerde camera technieken zijn beelden vast te leggen van fotosynthese activiteit en het is ook mogelijk gebleken om bladgedeelten met stress vast te leggen, zonder dat deze stress met het blote oog al te zien is. Dit opent perspectieven om monitorringonderzoek te doen naar het ontstaan van bladrandschade en tegelijkertijd naar de eventuele mogelijkheden tot ingrijpen met (wellicht) herstel. Deze metingen worden in het donker uitgevoerd. Er is recentelijk een nieuwe camera ontwikkeld die ook in het licht kan meten, maar bij een meting in het licht zal het verschil tussen schade- en gezonde plekken waarschijnlijk kleiner zijn dan bij een meting in het donker. Dit laatste zal getest moeten worden.
    Wondreacties van bomen : een literatuurstudie
    Reuver, E. - \ 1986
    Wageningen : De Dorschkamp (Rapport / Rijksinstituut voor Onderzoek in de Bos- en Landschapsbouw "De Dorschkamp" nr. 429) - 57
    bosbouw - hout - houteigenschappen - groeitempo - groeispanning - groeifactoren - groeieffecten - gebreken van hout - snoeien - overzichten - forestry - wood - wood properties - growth rate - growth stress - growth factors - growth effects - wood defects - pruning - reviews
    De volgende onderwerpen komen in deze literatuurstudie aan de orde: infectie en aantasting van het hout; reactie van de boom op verwonding; wondreacties in het kernhout en technieken van snoei- en wondbehandeling
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