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.

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Inactivation of chemical and heat-resistant spores of Bacillus and Geobacillus by nitrogen cold atmospheric plasma and comparison to thermal and chemical based methods
Bokhorst-van de Veen, H. van; Xie, H. ; Esveld, D.C. ; Abee, T. ; Mastwijk, H.C. ; Nierop Groot, M.N. - \ 2015
Food Microbiology 45 (2015)part A. - ISSN 0740-0020 - p. 26 - 33.
low-temperature - gas plasma - subtilis spores - sterilization - salmonella - decontamination - microorganisms - hypochlorite - germination
Bacterial spores are resistant to severe conditions and form a challenge to eradicate from food or food packaging material. Cold atmospheric plasma (CAP) treatment is receiving more attention as potential sterilization method at relatively mild conditions but the exact mechanism of inactivation is still not fully understood. In this study, the biocidal effect by nitrogen CAP was determined for chemical (hypochlorite and hydrogen peroxide), physical (UV) and heat-resistant spores. The three different sporeformers used are Bacillus cereus a food-borne pathogen, and Bacillus atrophaeus and Geobacillus stearothermophilus that are used as biological indicators for validation of chemical sterilization and thermal processes, respectively. The different spores showed variation in their degree of inactivation by applied heat, hypochlorite, hydrogen peroxide, and UV treatments, whereas similar inactivation results were obtained with the different spores treated with nitrogen CAP. G. stearothermophilus spores displayed high resistance to heat, hypochlorite, hydrogen peroxide, while for UV treatment B. atrophaeus spores are most tolerant. Scanning electron microscopy analysis revealed distinct morphological changes for nitrogen CAP-treated B. cereus spores including etching effects and the appearance of rough spore surfaces, whereas morphology of spores treated with heat or disinfectants showed no such changes. Moreover, microscopy analysis revealed CAP-exposed B. cereus spores to turn phase grey conceivably because of water influx indicating damage of the spores, a phenomenon that was not observed for non-treated spores. In addition, data are supplied that exclude UV radiation as determinant of antimicrobial activity of nitrogen CAP. Overall, this study shows that nitrogen CAP treatment has a biocidal effect on selected Bacillus and Geobacillus spores associated with alterations in spore surface morphology and loss of spore integrity.
High specific activity for anammox bacteria enriched from activated sludge at 10 °C
Hendrickx, T.L.G. ; Kampman, C. ; Zeeman, G. ; Temmink, B.G. ; Hu, Z. ; Kartal, B. ; Buisman, C.J.N. - \ 2014
Bioresource Technology 163 (2014). - ISSN 0960-8524 - p. 214 - 221.
anaerobic ammonium oxidation - autotrophic nitrogen removal - strength waste-water - low-temperature - granular sludge - marine-sediments - performance - sewage - scale - reactor
Anammox in the water line of a waste water treatment plant (WWTP) saves energy for aeration and allows for recovering biogas from organic material. Main challenges for applying the anammox process in the water line are related to the low temperature of
The effect of sludge recirculation rate on a UASB-digester treating domestic sewage at 15 °C
Zhang, L. ; Hendrickx, T.L.G. ; Kampman, C. ; Zeeman, G. ; Temmink, B.G. ; Weiguang Li, ; Buisman, C.J.N. - \ 2012
Water Science and Technology 66 (2012)12. - ISSN 0273-1223 - p. 2597 - 2603.
afvalwaterbehandeling - afvalwater - rioolwater - huishoudens - anaërobe behandeling - anaërobe verteerders - slibvergisting - recirculatiesystemen - temperatuur - zuurstofbehoefte - biogas - concentratie - efficiëntie - waste water treatment - waste water - sewage - households - anaerobic treatment - anaerobic digesters - sludge digestion - recirculating systems - temperature - oxygen requirement - concentration - efficiency - waste-water treatment - anaerobic-digestion - low-temperature
The anaerobic treatment of low strength domestic sewage at low temperature is an attractive and important topic at present. The upflow anaerobic sludge bed (UASB)-digester system is one of the anaerobic systems to challenge low temperature and concentrations. The effect of sludge recirculation rate on a UASB-digester system treating domestic sewage at 15 °C was studied in this research. A sludge recirculation rate of 0.9, 2.6 and 12.5% of the influent flow rate was investigated. The results showed that the total chemical oxygen demand (COD) removal efficiency rose with increasing sludge recirculation rate. A sludge recirculation rate of 0.9% of the influent flow rate led to organic solids accumulation in the UASB reactor. After the sludge recirculation rate increased from 0.9 to 2.6%, the stability of the UASB sludge was substantially improved from 0.37 to 0.15 g CH4-COD/g COD, and the bio­gas production in the digester went up from 2.9 to 7.4 L/d. The stability of the UASB sludge and bio­gas production in the digester were not significantly further improved by increasing sludge recirculation rate to 12.5% of the influent flow rate, but the biogas production in the UASB increased from 0.37 to 1.2 L/d. It is recommended to apply a maximum sludge recirculation rate of 2–2.5% of the influent flow rate in a UASB-digester system, as this still allows energy self-sufficiency of the system.
Identification of Reference Genes For RT-qPCR Expression Analysis In Arabidopsis And Tomato Seeds
Dekkers, S.J.W. ; Willems, L.A.J. ; Bassel, G. ; Bolderen-Veldkamp, R.P. van; Ligterink, W. ; Hilhorst, H.W.M. ; Bentsink, L. - \ 2012
Plant and Cell Physiology 53 (2012)1. - ISSN 0032-0781 - p. 28 - 37.
quantitative pcr data - real-time pcr - gibberellin biosynthesis - housekeeping genes - low-temperature - messenger-rna - abscisic-acid - data sets - germination - normalization
Quantifying gene expression levels is an important research tool to understand biological systems. Reverse transcription–quantitative real-time PCR (RT–qPCR) is the preferred method for targeted gene expression measurements because of its sensitivity and reproducibility. However, normalization, necessary to correct for sample input and reverse transcriptase efficiency, is a crucial step to obtain reliable RT–qPCR results. Stably expressed genes (i.e. genes whose expression is not affected by the treatment or developmental stage under study) are indispensable for accurate normalization of RT–qPCR experiments. Lack of accurate normalization could affect the results and may lead to false conclusions. Since transcriptomes of seeds are different from other plant tissues, we aimed to identify reference genes specifically for RT–qPCR analyses in seeds of two important seed model species, i.e. Arabidopsis and tomato. We mined Arabidopsis seed microarray data to identify stably expressed genes and analyzed these together with putative reference genes from other sources. In total, the expression stability of 24 putative reference genes was validated by RT–qPCR in Arabidopsis seed samples. For tomato, we lacked transcriptome data sets of seeds and therefore we tested the tomato homologs of the reference genes found for Arabidopsis seeds. In conclusion, we identified 14 Arabidopsis and nine tomato reference genes. This provides a valuable resource for accurate normalization of gene expression experiments in seed research for two important seed model species.
Carotenoid and fatty acid metabolism in nitrogen-starved Dunaliella salina, a unicellular green microalga
Lamers, P.P. ; Janssen, M. ; Vos, R.C.H. de; Bino, R.J. ; Wijffels, R.H. - \ 2012
Journal of Biotechnology 162 (2012)1. - ISSN 0168-1656 - p. 21 - 27.
beta-carotene - biochemical-composition - nutrient limitation - low-temperature - high light - accumulation - bardawil - alga - induction - stress
Nitrogen availability and light intensity affect ß-carotene overproduction in the green alga Dunaliella salina. Following a previous study on high-light stress, we here report on the effect of nitrogen depletion on the growth characteristics and ß-carotene as well as fatty acid metabolism of D. salina under a constant light regime in a turbidostat. Upon nitrogen depletion, the biomass yield on absorbed light approximately doubled, due to a transient increase in cell division rate, swelling of the cells and a linear increase of the density of the cells. Simultaneously, ß-carotene started to accumulate up to a final intracellular concentration of 14 mg LCV-1 (i.e. 2.7% of AFDW). This ß-carotene production accounted for 6% of the increased density of the cells, indicating that other biochemical constituents accumulated as well. Since D. salina accumulates ß-carotene in lipid globules, we also determined the fatty acid content and composition of D. salina. The intracellular concentration of the total fatty acid pool did not change significantly during nitrogen starvation, indicating that ß-carotene and total fatty acid accumulation were unrelated, similar to what was found previously for high-light treated cells. However, for both high-light and nitrogen stress, ß-carotene accumulation negatively correlated with the degree of unsaturation of the total fatty acid pool and, within the individual fatty acids, correlated positively with oleic acid biosynthesis, suggesting that oleic acid may be a key component of the lipid-globule-localized triacylglycerols and thereby in ß-carotene accumulation.
Complex genetics controls natural variation among seed quality phenotypes in a recombinant inbred population of an interspecific cross between Solanum lycopersicum × Solanum pimpinellifolium
Kazmi, R.H. ; Khan, N. ; Willems, L.A.J. ; Heusden, A.W. van; Ligterink, J.W. ; Hilhorst, H.W.M. - \ 2012
Plant, Cell & Environment 35 (2012)5. - ISSN 0140-7791 - p. 929 - 951.
quantitative trait loci - abiotic stress tolerance - abscisic-acid - arabidopsis-thaliana - qtl analysis - drought tolerance - salt tolerance - line population - low-temperature - water-stress
Seed quality in tomato is associated with many complex physiological and genetic traits. While plant processes are frequently controlled by the action of small- to large-effect genes that follow classic Mendelian inheritance, our study suggests that seed quality is primarily quantitative and genetically complex. Using a recombinant inbred line population of Solanum lycopersicum × Solanum pimpinellifolium, we identified quantitative trait loci (QTLs) influencing seed quality phenotypes under non-stress, as well as salt, osmotic, cold, high-temperature and oxidative stress conditions. In total, 42 seed quality traits were analysed and 120 QTLs were identified for germination traits under different conditions. Significant phenotypic correlations were observed between germination traits under optimal conditions, as well as under different stress conditions. In conclusion, one or more QTLs were identified for each trait with some of these QTLs co-locating. Co-location of QTLs for different traits can be an indication that a locus has pleiotropic effects on multiple traits due to a common mechanistic basis. However, several QTLs also dissected seed quality in its separate components, suggesting different physiological mechanisms and signalling pathways for different seed quality attributes.
Carotenoid and Fatty Acid Metabolism in Light-Stressed Dunaliella salina
Lamers, P.P. ; Laak, C.W. ; Kaasenbrood, P.S. ; Lorier, J. ; Janssen, M.G.J. ; Vos, C.H. de; Bino, R.J. ; Wijffels, R.H. - \ 2010
Biotechnology and Bioengineering 106 (2010)4. - ISSN 0006-3592 - p. 638 - 648.
beta-carotene - halotolerant alga - low-temperature - bardawil - salina - accumulation - marine - chlorophyta - microalgae - biotechnology
Carotene is overproduced in the alga Dunaliella salina in response to high light intensities. We have studied the effects of a sudden light increase on carotenoid and fatty acid metabolism using a flat panel photobioreactor that was run in turbidostat mode to ensure a constant light regime throughout the experiments. Upon the shift to an increased light intensity, -carotene production commenced immediately. The first 4 h after induction were marked by constant intracellular levels of -carotene (2.2 g LCV-1), which resulted from identical increases in the production rates of cell volume and -carotene. Following this initial phase, -carotene productivity continued to increase while the cell volume productivity dropped. As a result, the intracellular -carotene concentration increased reaching a maximum of 17 g LCV-1 after 2 days of light stress. Approximately 1 day before that, the maximum -carotene productivity of 30 pg cell-1 day-1 (equivalent to 37 mg LRV-1 day-1) was obtained, which was about one order of magnitude larger than the average productivity reported for a commercial -carotene production facility, indicating a vast potential for improvement. Furthermore, by studying the light-induced changes in both -carotene and fatty acid metabolism, it appeared that carotenoid overproduction was associated with oil globule formation and a decrease in the degree of fatty acid unsaturation. Our results indicate that cellular -carotene accumulation in D. salina correlates with accumulation of specific fatty acid species (C16:0 and C18:1) rather than with total fatty acid content
The Selectivity of Milking of Dunaliella salina
Kleinegris, D.M.M. ; Janssen, M.G.J. ; Brandenburg, W.A. ; Wijffels, R.H. - \ 2010
Marine Biotechnology 12 (2010)1. - ISSN 1436-2228 - p. 14 - 23.
beta-carotene production - 2-phase bioreactors - low-temperature - photosystem-ii - green-algae - accumulation - bardawil - chlorophyll - extraction - protein
The process of the simultaneous production and extraction of carotenoids, milking, of Dunaliella salina was studied. We would like to know the selectivity of this process. Could all the carotenoids produced be extracted? And would it be possible to vary the profile of the produced carotenoids and, consequently, influence the type of carotenoids extracted? By using three different D. salina strains and three different stress conditions, we varied the profiles of the carotenoids produced. Between Dunaliella bardawil and D. salina 19/18, no remarkable differences were seen in the extraction profiles, although D. salina 19/18 seemed to be better extractable. D. salina 19/25 was not “milkable” at all. The milking process could only be called selective for secondary carotenoids in case gentle mixing was used. In aerated flat-panel photobioreactors, extraction was much better, but selectiveness decreased and also chlorophyll and primary carotenoids were extracted. This was possibly related to cell damage due to shear stress
A cold treatment promotes both sprouting and sink strength of lily bulblets
Klerk, G.J.M. de - \ 2009
Propagation of ornamental plants 9 (2009)2. - ISSN 1311-9109 - p. 102 - 106.
regenerated in-vitro - low-temperature - dormancy development - abscisic-acid - invitro - pathways - growth - potato - tulip - induction
Lily bulblets produced in tissue culture at 20 or 25ºC are cold-treated before planting to break dormancy. Bulblets produced in tissue culture at a relatively low temperature (15ºC), though, are nondormant and sprout without a preceding cold treatment. Leaves generated after planting by noncold-treated 15ºC bulblets, were relatively small and as a consequence bulblet growth after planting was limited. This was also observed for the few 20 and 25ºC bulblets that did sprout without a cold treatment. Sink-strength of bulblets was assessed as bulblet dry-weight (DW) gain per mg leaf DW. Noncold-treated bulblets had far less sink-strength than cold-treated ones. Thus, a second cause of the little growth of noncold-treated bulblets was their small sink-strength. The optimal temperatures to break dormancy and to promote sink strength were 9 and 2ºC, respectively. It is concluded that a cold treatment not only breaks dormancy but also enhances sink strength, and that these are unrelated processes.
Adapting UASB technology for sewage treatment in Palestine and Jordan
Mahmoud, N.A. ; Zeeman, G. ; Lier, J.B. van - \ 2008
Water Science and Technology 57 (2008)3. - ISSN 0273-1223 - p. 361 - 366.
afvalwaterbehandeling - anaërobe behandeling - rioolwater - tropisch klimaat - aanpassing - jordanië - zuiveringsinstallaties - palestina - waste water treatment - anaerobic treatment - sewage - tropical climate - adjustment - jordan - purification plants - palestine - domestic sewage - low-temperature - waste-water - reactor
High rate anaerobic technologies offer cost-effective solutions for "sewage" treatment in the temperate climate of Palestine and Jordan. However, local sewage characteristics demand amendments to the conventional UASB reactor design. A solution is found in a parallel operating digester unit that stabilises incoming solids and enriches the UASB sludge bed with methanogenic activity. The digester operational conditions were assessed by operating eight CSTRs fed with primary sludge. The results showed a high degree of sludge stabilization in the parallel digesters at SRTs10 and 15 days at process temperatures of 35 and 25°C, respectively. The technical feasibility of the UASB-digester combination was demonstrated by continuous flow pilot-scale experiments. A pilot UASB reactor was operated for 81 days at 6 hours HRT and 15°C and was fed with raw domestic sewage. This period was subsequently followed by an 83 day operation period incorporating a parallel digester unit, which was operated at 35°C. The UASB-digester combination achieved removal efficiencies of total, suspended, colloidal and dissolved CODs of respectively 66, 87, 44 and 30%. Preliminary model calculations indicated that a total reactor volume of the UASB-digester system corresponding to 8.6 hours HRT might suffice for sewage treatment in Palestine
SodERF3, a novel sugarcane ethylene responsive factor (ERF), enhances salt and drought tolerance when overexpressed in tobacco plants
Trujillo, L.E. ; Sotolongo, M. ; Menéndez, C. ; Ochogavía, M.E. ; Coll, Y. ; Hernández, I. ; Borrás-Hidalgo, O. ; Thomma, B.P.H.J. ; Vera, P. ; Hernández, L. - \ 2008
Plant and Cell Physiology 49 (2008)4. - ISSN 0032-0781 - p. 512 - 525.
transcription factor gene - element-binding factors - disease resistance - low-temperature - abscisic-acid - arabidopsis-thaliana - signal-transduction - pathogen infection - stress responses - osmotic-stress
The molecular signals and pathways that govern biotic and abiotic stress responses in sugarcane are poorly understood. Here we describe SodERF3, a sugarcane (Saccharum officinarum L. cv Ja60-5) cDNA that encodes a 201-amino acid DNA-binding protein that acts as a transcriptional regulator of the ethylene responsive factor (ERF) superfamily. Like other ERF transcription factors, the SodERF3 protein binds to the GCC box, and its deduced amino acid sequence contains an N-terminal putative nuclear localization signal (NLS). In addition, a C-terminal short hydrophobic region that is highly homologous to an ERF-associated amphiphilic repression-like motif, typical for class II ERFs, was found. Northern and Western blot analysis showed that SodERF3 is induced by ethylene. In addition, SodERF3 is induced by ABA, salt stress and wounding. Greenhouse-grown transgenic tobacco plants (Nicotiana tabacum L. cv. SR1) expressing SodERF3 were found to display increased tolerance to drought and osmotic stress.
Insights on the development, kinetics, and variation of photoinhibition using chlorophyll fluorescence imaging af a chilled, variegated leaf
Hogewoning, S.W. ; Harbinson, J. - \ 2007
Journal of Experimental Botany 58 (2007)3. - ISSN 0022-0957 - p. 453 - 463.
acclimated spinach leaves - mangifera-indica l. - cucumis-sativus - low-temperature - zea-mays - photosynthesis - plants - susceptibility - inhibition - transport
The effect of chilling on photosystem II (PSII) efficiency was studied in the variegated leaves of Calathea makoyana, in order to gain insight into the causes of chilling-induced photoinhibition. Additionally, a relationship was revealed between (chilling) stress and variation in photosynthesis. Chilling treatments (5 degrees C and 10 degrees C) were performed for different durations (1-7 d) under a moderate irradiance (120 mu mol m(-2) s(-1)). The individual leaves were divided into a shaded zone and two illuminated, chilled zones. The leaf tip and sometimes the leaf base were not chilled. Measurements of the dark-adapted F-v/F-m were made on the different leaf zones at the end of the chilling treatment, and then for several days thereafter to monitor recovery. Chilling up to 7 d in the dark did not affect PSII efficiency and visual appearance, whereas chilling in the light caused severe photoinhibition, sometimes followed by leaf necrosis. Photoinhibition increased with the duration of the chilling period, whereas, remarkably, chilling temperature had no effect. In the unchilled leaf tip, photoinhibition also occurred, whereas in the unchilled leaf base it did not. Whatever the leaf zone, photoinhibition became permanent if the mean value dropped below 0.4, although chlorosis and necrosis were associated solely with chilled illuminated tissue. Starch accumulated in the unchilled leaf tip, in contrast to the adjacent chilled irradiated zone. This suggests that photoinhibition was due to a secondary effect in the unchilled leaf tip (sink limitation), whereas it was a direct effect of chilling and irradiance in the chilled illuminated zones. The PSII efficiency and its coefficient of variation showed a unique negative linearity across all leaf zones and different tissue types. The slope of this curve was steeper for chilled leaves than it was for healthy, non-stressed leaves, suggesting that the coefficient of variation may be an important tool for assessing stress in leaves.
Assessing risks of releasing exotic biological control agents of arthropod pests
Lenteren, J.C. van; Bale, J.S. ; Bigler, F. ; Hokkanen, H.M.T. ; Loomans, A.J.M. - \ 2006
Annual Review of Entomology 51 (2006). - ISSN 0066-4170 - p. 609 - 634.
apparent competition - typhlodromips-montdorensis - intraguild predation - biocontrol agent - low-temperature - weed-control - uk - dispersal - parasitoids - insects
Abstract More than 5000 introductions of about 2000 species of exotic arthropod agents for control of arthropod pests in 196 countries or islands during the past 120 years rarely have resulted in negative environmental effects. Yet, risks of environmental effects caused by releases of exotics are of growing concern. Twenty countries have implemented regulations for release of biological control agents. Soon, the International Standard for Phytosanitary Measures (ISPM3) will become the standard for all biological control introductions worldwide, but this standard does not provide methods by which to assess environmental risks. This review summarizes documented nontarget effects and discusses the development and application of comprehensive and quick-scan environmental risk assessment methods
The role of sigmaB in the stress response of Gram-positive bacteria - targets for food preservation and safety
Schaik, W. van; Abee, T. - \ 2005
Current Opinion in Biotechnology 16 (2005)2. - ISSN 0958-1669 - p. 218 - 224.
listeria-monocytogenes sigma(b) - staphylococcus-aureus - bacillus-subtilis - transcription factor - biofilm formation - functional rsbu - low-temperature - acid tolerance - sigb operon - heat-shock
The alternative sigma factor ¿B modulates the stress response of several Gram-positive bacteria, including Bacillus subtilis and the food-borne human pathogens Bacillus cereus, Listeria monocytogenes and Staphylococcus aureus. In all these bacteria, ¿B is responsible for the transcription of genes that can confer stress resistance to the vegetative cell. Recent findings indicate that ¿B also plays an important role in antibiotic resistance, pathogenesis and cellular differentiation processes such as biofilm formation and sporulation. Although there are important differences in the regulation of ¿B and in the set of genes regulated by ¿B in B. subtilis, B. cereus, L. monocytogenes and S. aureus, there are also some conserved themes. A mechanistic understanding of the ¿B activation processes and assessment of its regulon could provide tools for pathogen control and inactivation both in the food industry and clinical settings
Genetic and molecular analyses of natural variation indicate CBF2 as a candidate gene for underlying a freezing tolerance quantitative trait locus in Arabidopsis
Alonso-Blanco, C. ; Gomez-Mena, C. ; Llorente, F. ; Koornneef, M. ; Salinas, J. ; Martinez-Zapater, J.M. - \ 2005
Plant Physiology 139 (2005)3. - ISSN 0032-0889 - p. 1304 - 1312.
cold-response pathway - low-temperature - allelic variation - flowering time - transcriptional activators - signal-transduction - stress tolerance - thaliana - expression - acclimation
Natural variation for freezing tolerance is a major component of adaptation and geographic distribution of plant species. However, little is known about the genes and molecular mechanisms that determine its naturally occurring diversity. We have analyzed the intraspecific freezing tolerance variation existent between two geographically distant accessions of Arabidopsis (Arabidopsis thaliana), Cape Verde Islands (Cvi) and Landsberg erecta (Ler). They differed in their freezing tolerance before and after cold acclimation, as well as in the cold acclimation response in relation to photoperiod conditions. Using a quantitative genetic approach, we found that freezing tolerance differences after cold acclimation were determined by seven quantitative trait loci (QTL), named FREEZING TOLERANCE QTL 1 (FTQ1) to FTQ7. FTQ4 was the QTL with the largest effect detected in two photoperiod conditions, while five other FTQ loci behaved as photoperiod dependent. FTQ4 colocated with the tandem repeated genes C-REPEAT BINDING FACTOR 1 (CBF1), CBF2, and CBF3, which encode transcriptional activators involved in the cold acclimation response. The low freezing tolerance of FTQ4-Cvi alleles was associated with a deletion of the promoter region of Cvi CBF2, and with low RNA expression of CBF2 and of several CBF target genes. Genetic complementation of FTQ4-Cvi plants with a CBF2-Ler transgene suggests that such CBF2 allelic variation is the cause of CBF2 misexpression and the molecular basis of FTQ4
Differentially expressed genes associated with dormancy or germination of Arabidopsis thaliana seeds
Toorop, P.E. ; Barroco, R.M. ; Engler, G. ; Groot, S.P.C. ; Hilhorst, H.W.M. - \ 2005
Planta 221 (2005)5. - ISSN 0032-0935 - p. 637 - 647.
zaadkieming - genen - genexpressie - seed germination - genes - gene expression - ribosomal-protein genes - low-temperature - abscisic-acid - l heynh - gibberellins - desiccation - pathways - mutants - bodies - light
Differential display analysis using dormant and non-dormant Arabidopsis thaliana (L.) Heynh seeds resulted in a set of genes that were associated with either dormancy or germination. Expression of the germination-associated genes AtRPL36B and AtRPL27B, encoding two ribosomal proteins, was undetectable in the dry seed, low in dormant seed, and high under conditions that allowed completion of germination. Expression of these genes was also found to be light-regulated and to correlate with germination speed. Expression of the dormancy-associated genes ATS2 and ATS4, encoding a caleosin-like protein and a protein similar to a low-temperature-induced protein respectively, was high in the dry seed and decreased during germination. Expression of ATS2 and ATS4 was high in primary and secondary dormant seed but low in after-ripened or chilled seed. The expression of both genes was also light-regulated, but no relationship with temperature-dependent germination speed was found.
Regeneration patterns in boreal Scots pine glades linked to cold-induced photoinhibition
Slot, M. ; Wirth, C. ; Schumacher, J. ; Mohren, G.M.J. ; Shibistova, O. ; Lloyd, J. ; Ensminger, I. - \ 2005
Tree Physiology 25 (2005). - ISSN 0829-318X - p. 1139 - 1150.
dependent energy-dissipation - xanthophyll cycle - alpine-treeline - low-temperature - snow gum - seedlings - growth - plants - light - photosynthesis
Summary Regeneration patterns of Pinus sylvestris L. juveniles in central Siberian glades were studied in relation to cold-induced photoinhibition. Spatial distribution of seedlings in different height classes revealed higher seedling densities beneath the canopy than beyond the canopy, and significantly higher densities of seedlings <50 cm tall on the north side of the trees. These patterns coincided with differences in light conditions. Compared with plants on the north side of canopy trees (north-exposed), photosynthetic photon flux (PPF) received by plants on the south side of canopy trees (south-exposed) was always higher, making south-exposed plants more susceptible to photoinhibition, especially on cool mornings. Chlorophyll fluorescence data revealed lower photochemical efficiency and increased non-photochemical quenching of small (20-50 cm in height), south-exposed seedlings from spring to early autumn, indicating increased excitation pressure on photosynthesis. Maximum rate of oxygen evolution was less in south-exposed plants than in north-exposed plants. Increased pools of xanthophyll cycle pigments and formation of the photoprotective zeaxanthin provided further evidence for the higher susceptibility to photoinhibition of south-exposed seedlings. A linear mixed model analysis explained many of the physiological differences observed in seedlings according to height class and aspect with early morning temperature and PPF as predictors. The link between photoinhibition and differential distribution of seedlings by height class suggests that photoinhibition, together with other environmental stresses, decreases the survival of small, south-exposed P. sylvestris seedlings, thereby significantly affecting the regeneration pattern of central Siberian pine glades. Keywords: environmental stress, excitation pressure, Pinus sylvestris, Siberia, xanthophyll cycle.
Anaerobic sewage treatment in a one-stage UASB reactor and a combined UASB Digester system
Mahmoud, N.A. ; Zeeman, G. ; Gijzen, H.J. ; Lettinga, G. - \ 2004
Water Research 38 (2004)9. - ISSN 0043-1354 - p. 2348 - 2358.
domestic sewage - waste-water - de-waterability - low-temperature - sludge - wastewaters - particles
The treatment of sewage at 15°C was investigated in a one-stage upflow anaerobic sludge blanket (UASB) reactor and a UASB-Digester system. The latter consists of a UASB reactor complemented with a digester for mutual sewage treatment and sludge stabilisation. The UASB reactor was operated at a hydraulic retention time of 6 h and a controlled temperature of 15°C, the average sewage temperature during wintertime of some Middle East countries. The digester was operated at 35°C. The UASB-Digester system provided significantly (significance level 5%) higher COD removal efficiencies than the one-stage UASB reactor. The achieved removal efficiencies in the UASB-Digester system and the one-stage UASB reactor for total, suspended, colloidal and dissolved COD were 66%, 87%, 44% and 30%, and 44%, 73%, 3% and 5% for both systems, respectively. The stability values of the wasted sludge from the one-stage UASB reactor and the UASB-Digester system were, respectively, 0.47 and 0.36 g CH4-COD/g COD. Therefore, the anaerobic sewage treatment at low temperature in a UASB-Digester system is promising
Identification of sigma factor SigmaB-controlled genes and their impact on acid stress, high hydrostatic pressure, and freeze survival in Listeria monocytogenes EGD-e
Wemekamp-Kamphuis, H.H. ; Wouters, J.A. ; Leeuw, P.P.L.A. de; Hain, T. ; Chakraborty, T. ; Abee, T. - \ 2004
Applied and Environmental Microbiology 70 (2004)6. - ISSN 0099-2240 - p. 3457 - 3466.
bacillus-subtilis - tolerance response - low-temperature - resistance - virulence - growth - transcription - adaptation - macrophages - expression
The gene encoding the alternative sigma factor sigma(B) in Listeria monocytogenes is induced upon exposure of cells to several stresses. In this study, we investigated the impact of a sigB null mutation on the survival of L. monocytogenes EGD-e at low pH, during high-hydrostatic-pressure treatment, and during freezing. The survival of DeltasigB mutant exponential-phase cells at pH 2.5 was 10,000-fold lower than the survival of EGD-e wild-type cells. Moreover, the DeltasigB mutant failed to show an acid tolerance response. Upon preexposure for 1 h to pH 4.5, the survival at pH 2.5 was 100,000-fold lower for the DeltasigB mutant than for the wild type. The glutamate decarboxylase (GAD) acid resistance system is important in survival and adaptation of L. monocytogenes in acidic conditions. The sigmaB dependence of the gad genes (gadA, gadB, gadC, gadD, and gadE) was analyzed in silico. Putative or sigma(B)-dependent promoter sites were found upstream of the gadCB operon (encoding a glutamate/gamma-aminobutyrate antiporter and a glutamate decarboxylase, respectively) and the lmo2434 gene (gadD, encoding a putative glutamate decarboxylase). Reverse transcriptase PCR revealed that expression of the gadCB operon and expression of gadD are indeed sigma(B) dependent. In addition, a proteomics approach was used to analyze the protein expression profiles upon acid exposure. Although the GAD proteins were not recovered, nine proteins accumulated in the wild type but not in the DeltasigB strain. These proteins included Pfk, GalE, ClpP, and Lmo1580. Exposure to pH 4.5, in order to preload cells with active sigma(B) and consequently with sigma(B)-dependent general stress proteins, also provided considerable protection against high-hydrostatic-pressure treatment and freezing. The combined data argue that the expression of or sigma(B)-dependent genes provides L. monocytogenes with nonspecific multiple-stress resistance that may be relevant for survival in the natural environment as well as during food processing.
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